# Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Western Distinct Population Segment of the Yellow-billed Cuckoo (Coccyzus americanus)

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2014-23640

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** October 3, 2014
- **Citation:** 79 FR 59992

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8- ES-2013-0104; 4500030113]
RIN 1018-AY53
Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Western Distinct Population Segment of the Yellow-billed Cuckoo (Coccyzus americanus)

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Final rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), determine threatened status under the Endangered Species Act of 1973 (Act), as amended, for the western distinct population segment (DPS) of the yellow-billed cuckoo (
Coccyzus americanus
), a species located from the western portions of the United States, Canada, and Mexico. This final rule implements the Federal protections provided by the Act for this DPS.

DATES:

This rule is effective November 3, 2014.

ADDRESSES:

This final rule is available on the Internet at
http://www.regulations.gov
and at the Sacramento Fish and Wildlife Office at
http://www.fws.gov/sacramento/.
Comments and materials received, as well as supporting documentation used in the preparation of this rule, will be available for public inspection, by appointment, during normal business hours at: U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Room W-2605, Sacramento, CA 95825; by telephone 916-414- 6600; or by facsimile 916- 414-6712.

FOR FURTHER INFORMATION CONTACT:

Jennifer Norris, Field Supervisor, Sacramento Fish and Wildlife Office (see
ADDRESSES
). If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800- 877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule.
Under the Endangered Species Act, a species may warrant protection through listing if it is endangered or threatened throughout all or a significant portion of its range. Listing a species as an endangered or threatened species can only be completed by issuing a rule. On October 3, 2013, we published in the
Federal Register
a proposed rule (78 FR 61621) to list the western DPS of the yellow-billed cuckoo (hereafter referred to as western yellow-billed cuckoo). This rule finalizes our determination for listing the western yellow-billed cuckoo.

The basis for our action.
Under the Endangered Species Act, we can determine that a species is an endangered or threatened species based on any of five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence.

We have determined that the western yellow-billed cuckoo meets the definition of a threatened species and is likely to become endangered throughout its range within the foreseeable future, based on the immediacy, severity, and scope of the threats to its continued existence. These include habitat loss associated with manmade features that alter watercourse hydrology so that the natural processes that sustained riparian habitat in western North America are greatly diminished. Loss and degradation of habitat has also occurred as a result of livestock overgrazing and encroachment from agriculture. These losses are exacerbated by the conversion of native habitat to predominantly nonnative vegetation. Habitat loss results in the additional effects associated with small and widely separated habitat patches such as increased predation and reduced dispersal potential. This threat is particularly persistent where small habitat patches are in proximity to human-altered landscapes, especially agricultural fields, resulting in the potential for pesticides to poison individual western yellow-billed cuckoos and reduce their prey base.

What the rule does.
We are making a final listing determination regarding the western distinct population segment of the U.S. population of the yellow-billed cuckoo pursuant to the Endangered Species Act. This species occurs in the western United States, Canada, and Mexico. The western U.S. States include Washington, Idaho, Montana, Oregon, California, Nevada, Wyoming, Utah, Colorado, Arizona, New Mexico, and Texas. This document adds the western DPS of the yellow-billed cuckoo (
Coccyzus americanus
) as a threatened species to the List of Endangered and Threatened Wildlife (50 CFR 17.11(h)).

Peer review and public comment.
We sought comments from independent specialists to ensure that our determination is based on scientifically sound data, assumptions, and analyses. We invited these peer reviewers to comment on our listing proposal. We also considered all other comments and information we received during the three open comment periods. We have considered and incorporated any pertinent information from all comments and information we received into this final rule. See the
Summary of Comments and Recommendations
section, below, for a summary of comments we received on the proposed listing.

Previous Federal Actions

On October 3, 2013, the proposed rule to list the western yellow-billed cuckoo as a threatened species under section 4 of the Act (16 U.S.C. 1531
et seq.
) was published in the
Federal Register
(78 FR 61621). This rule finalizes the Federal action for this species. For additional information on previous Federal actions for the western yellow-billed cuckoo, please see the 12-month petition finding (66 FR 38611; July 25, 2001) and proposed listing rule (78 FR 61621; October 3, 2013).

We proposed critical habitat for the western DPS of the yellow-billed cuckoo on August 15, 2014 (79 FR 48547).

Background

In this section of the final rule, it is our intent to discuss only those topics directly relevant to the listing of the western yellow-billed cuckoo as a threatened species. Please refer to the proposed listing rule for the western yellow-billed cuckoo for detailed background and species information (78 FR 61621; October 3, 2013).

Species Information

The yellow-billed cuckoo (
Coccyzus americanus
) is a member of the avian family Cuculidae and is a Neotropical migrant bird that winters in South America and breeds in North America. Yellow-billed cuckoos spend the winter in South America, east of the Andes, primarily south of the Amazon Basin in southern Brazil, Paraguay, Uruguay, eastern Bolivia, and northern Argentina (Ehrlich
et al.
1992, pp. 129-130; American Ornithologists' Union (AOU) 1998, p. 247; Johnson
et al.
2008b, pp. 18-29). The breeding range of the entire species formerly included most of North America from southeastern and western Canada (southern Ontario, Quebec, and southwestern British Columbia) south throughout the continental United States to the Greater Antilles and

northern Mexico (AOU 1957, pp. 269-270; AOU 1983, p. 284; AOU 1998, p. 247). Currently, the species no longer breeds in western Canada and the northwestern continental United States (Washington, Oregon, and Montana).

Adult yellow-billed cuckoos have a fairly stout and slightly down-curved bill; a slender, elongated body with a long-tailed look; and a narrow yellow ring of colored, bare skin around the eye. The plumage is loose and grayish-brown above and white below, with reddish primary flight feathers. The tail feathers are boldly patterned with black and white below. They are a medium-sized bird about 12 inches (in) (30 centimeters (cm)) in length, and about 2 ounces (oz) (60 grams (g)) in weight. The bill is blue-black with yellow on the basal half of the lower mandible. The legs are short and bluish-gray. All cuckoos have a zygodactyl foot with two toes pointing forwards and two toes pointing backwards. Juvenile yellow-billed cuckoos resemble adults, except the tail patterning is less distinct and the lower bill has little or no yellow. Males and females differ slightly and are indistinguishable in the field (Hughes 1999, pp. 2-3).

Typically a secretive and hard-to-detect bird, adult yellow-billed cuckoos have a distinctive “kowlp” call, which is a loud, nonmusical series of notes that slows down and slurs toward the end. Yellow-billed cuckoos advertise for a mate using a series of soft “cooing” notes, which they give at night as well as during daytime. Both members of a pair use a soft knocking call as a contact or warning call near the nest (Hughes 1999, pp. 8-9). Please refer to the October 3, 2013, proposed listing rule (78 FR 61623-61642) for additional species information.

Taxonomy

Recent research on yellow-billed cuckoo genetics using mitochondrial DNA did not find any fixed genetic differences between eastern and western yellow-billed cuckoos (Farrell 2013, pp. 165-170). The author concluded that the separation into distinct subspecies may be too recent to be expressed in a single mitochondrial gene and recommended future studies using next-generation sequencing techniques. Avian geneticist Janice Hughes, Ph.D., a peer reviewer of the proposed listing rule, concluded that close examination of the DNA studies conducted to date on cuckoos infers a deeper genetic divergence between western and eastern cuckoos that with further analysis would likely support division of the yellow-billed cuckoo into two subspecies. She indicated that genetic markers used in all three previously conducted genetics studies evolve too slowly to reveal genetic structure within the species. She recommended that future studies use microsatellite techniques because they would be more informative to a study of DNA at the subspecies level. The existing DNA studies, however, show that western yellow-billed cuckoos have developed unique genetic haplotypes not present in eastern cuckoos and that these are reflected in phenotypic (outwardly visible) divergence that has been observed between eastern and western yellow-billed cuckoos. Please refer to the October 3, 2013, proposed listing rule (78 FR 61624-61645) for a more detailed discussion of information on taxonomy for the species.

Distinct Vertebrate Population Segment Analysis

Under the Act, we must consider listing any species, subspecies, or, for vertebrates, any DPS of these taxa if there is sufficient information to indicate that such action may be warranted. To implement the measures prescribed by the Act and its Congressional guidance, we (along with the National Marine Fisheries Service) developed policy that addresses the recognition of DPSs for potential listing actions (61 FR 4722; February 7, 1996). The policy allows for more refined application of the Act that better reflects the biological needs of the taxon being considered, and avoids the inclusion of entities that do not require its protective measures.

Before we can evaluate whether a given population segment is a DPS under the Act, we must first determine if any population segments exist for the vertebrate species. As discussed in the
Taxonomy
section of the proposed rule (78 FR 61621; October 3, 2013), much of the available scientific information supports the yellow-billed cuckoos that nest in western North America as a biologically separate population segment.

To establish the range of the population segment under consideration, we used the area occupied by the western yellow-billed cuckoo (the subspecies) originally defined by Ridgway (1887, p. 273) and later refined by other researchers (AOU 1957, pp. 269-270; Oberholser and Kincaid 1974, pp. 434-435; Hughes 1999, Figure 1). After careful consideration of other possible population segment configurations, we determined that the Continental Divide (generally the crest of the Rocky Mountains based on watershed boundaries), the watershed divide between the Rio Grande and Pecos River, and the Chihuahuan Desert in Mexico was the best division between eastern and western populations. The area that we are considering occupied by the potential western DPS for the yellow-billed cuckoo is closely aligned with the traditionally defined range of the western yellow-billed cuckoo subspecies as partially described in the July 25, 2001, 12-month finding (66 FR 38611). Our goal is to determine if this western population meets the criteria of a DPS and, if so, whether the range boundaries identified in the literature are appropriate for the boundary of the DPS. This DPS analysis is based solely on the range during the breeding season because the migration route and winter range of western yellow-billed cuckoos are poorly known.

The geographical breeding range of the yellow-billed cuckoo in western North America includes suitable habitat within the low- to moderate-elevation areas west of the crest of the Rocky Mountains in Canada, Mexico, and the United States, including the upper and middle Rio Grande, the Colorado River Basin, the Sacramento and San Joaquin River systems, the Columbia River system, and the Fraser River. In Mexico, the range includes the Cape Region of Baja California Sur, and river systems in the Mexican States of Sonora, Sinaloa, western Chihuahua, and northwestern Durango. Eastern yellow-billed cuckoos (
Coccyzus americanus americanus
) breed east of the Rocky Mountains; north to North Dakota and southern Ontario, Canada; south to eastern Mexico; and on the islands of the Caribbean (AOU 1957, pp. 269-270) (Figure 1).

ER03OC14.004

Under our DPS policy, three elements are considered in a decision regarding the status of a possible DPS as endangered or threatened under the Act. The elements are: (1) Discreteness of the population segment in relation to the remainder of the species to which it belongs; (2) the significance of the population segment to the species to which it belongs; and (3) the population segment's conservation status in relation to the Act's standards for listing. In other words, if we determine that a population segment of a vertebrate species being considered for listing is both discrete and significant, we would conclude that it represents a DPS, and thus a “species” under section 3(16) of the Act, whereupon we would evaluate the level of threat to the DPS based on the five listing factors established under section 4(a)(1) of the Act to determine whether listing the DPS as an “endangered species” or a “threatened species” is warranted.

Below, we evaluate under our DPS policy whether the population segment of yellow-billed cuckoos that occurs in the western United States, northwestern Mexico, and southwestern Canada qualifies as a DPS under the Act.

Discreteness

Under our DPS Policy, a population segment of a vertebrate species may be considered discrete if it satisfies either of the following two conditions: (1) It is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors (quantitative measures of genetic or morphological discontinuity may provide evidence of this separation); or (2) it is delimited by international governmental boundaries within which significant differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the Act.

The analysis of the population segment of the yellow-billed cuckoo in western North America is based on the first of those two conditions, the marked separation from other populations. From southwest British Columbia along the Canadian border to the southern end of the Sangre de Cristo Mountains in northern New Mexico, nesting yellow-billed cuckoos in western North America are separated from nesting yellow-billed cuckoos in eastern North America by the high-elevation zone of the Rocky Mountains. Yellow-billed cuckoos breed both east and west of the crest of the Rocky Mountains, where suitable habitat occurs (Johnsgard 1986, p. 201). We generally define the crest of the Rocky Mountains and Continental Divide as the high-elevation zone between the drainages flowing west and east in the United States, Canada, and Mexico, although some areas such as near the Sangre de Cristo Range in southern Colorado and northern New Mexico is east of the east-flowing Rio Grande River. The division between the western and eastern population segments spans a distance of about 2,200 miles (mi) (3,540 kilometers (km)) from southwest British Columbia near the Canadian border along the crest of the Rocky Mountains based on watershed boundaries, south along the Rio Grande-Pecos Rivers watershed divide to the United States-Mexico border in the Big Bend area of Texas, then into Mexico along the eastern and southern boundaries of the State of Chihuahua south to the southern border of the State of Durango and to the Pacific Ocean along the southern border of the State of Sinaloa. The distance of separation between breeding yellow-

billed cuckoos in the east and west varies along this division from 160 mi (257 km) to more than 400 mi (644 km), and consists entirely of areas of unoccupied, unsuitable habitat for breeding yellow-billed cuckoos. The one exception to this distance of separation is along the Rio Grande in Brewster County, in southwestern Texas, where eastern yellow-billed cuckoos breed as far west as Rio Grande Village and western yellow-billed cuckoos are found upstream along the river approximately 50 mi (80 km) to the west.

Yellow-billed cuckoos historically bred at the southern tip of Vancouver Island and in the Fraser River valley north to Kamloops in southwestern British Columbia, Canada (Bent 1940, p. 64; Campbell
et al.
1990, p. 481). The species was apparently never common, with 23 records (18 specimen and 5 sight records) between 1881 and 1927. Two of these observations were of pairs believed to be nesting but not confirmed. Since the 1920s, the species has been recorded five times in British Columbia, with four of those records occurring since 1990 from the eastern half of the Province in areas not considered breeding habitat (Campbell
et al.
1990, p. 481; Siddle 1992, p. 1169; Cornell Lab of Ornithology 2012). Today, the species is considered extirpated as a breeder from the Province, but adult, nonbreeding individuals still occur irregularly (British Columbia Conservation Data Centre 2013).

In the northern Rocky Mountains and northern Great Plains—from the Canada border south through Colorado—the yellow-billed cuckoo is “extremely rare and local” as a breeding bird both east and west of the Rocky Mountains (Hughes 1999, p. 3). While the species breeds locally in river valleys in southern Idaho, southwestern Wyoming, western Colorado, and in Utah (Hughes 1999, pp. 1-3), it is quite rare or absent within the higher Rocky Mountains (Johnsgard 1986, p. 201). An examination of the distributional records for the Rocky Mountain region indicates that the area has had few records of yellow-billed cuckoos and the species is even scarcer at elevations above approximately 6,000 feet (ft) (1,850 meters (m)), and almost never breeds above 7,000 ft (2,154 m) (Bailey 1928, pp. 307-309; Phillips
et al.
1964, p. 45; Bailey and Niedrach 1965, pp. 404-406; Johnsgard 1986, p. 201; Corman and Magill 2000, pp. 10, 15; Howe and Hanberg 2000, p. 1-20). Exceptions to the elevational limit do occur and recent records of yellow-billed cuckoos have been confirmed above 6,000 ft (1,850 m) in the areas of Lower Green River Basin from the Seedskadee National Wildlife Refuge (NWR) to the Flaming Gorge Reservoir and west to the Bear River Drainage in Wyoming; along the Yampa River near Craig in northwest Colorado, and the Rio Grande River near Del Norte, and San Luis Valley of south-central Colorado; and the Henry's Fork River in Utah and Wyoming. Nevertheless, most of the crest of the Rocky Mountains includes a wide region of higher elevation where habitat for the species does not occur. In Colorado and Wyoming, the region above 6,000 ft (1,850 m) is typically more than 150 mi (240 km) wide on an east-west axis (Oxford 1995, p. 82).

The separation of the western yellow-billed cuckoo population segment from yellow-billed cuckoos in the eastern population segment continues south along the crest of the Rockies into southern Colorado and northern New Mexico, then the Rocky Mountains end and the separation is along the watershed boundary between the Rio Grande and the Pecos Rivers in central New Mexico (Sangre de Cristo Mountains), and southwest Texas, terminating at the Rio Grande in the Big Bend National Park. In this region, the eastern and western yellow-billed cuckoo populations are separated by arid basins and isolated mountain ranges that emerge from a high desert plateau. These mountain ranges from north to south include the Sangre de Cristo Mountains and Sacramento Mountains in central and southern New Mexico, the Guadalupe Mountains and Delaware Mountains on the Texas-New Mexico border, and the Davis Mountains, Del Norte Mountains, and Santiago Mountains in western Texas south to the Chisos Mountains in the Big Bend National Park on the border with Mexico.

In southern New Mexico and western Texas where western yellow-billed cuckoos nest along the Rio Grande and eastern yellow-billed cuckoos nest along the Pecos River, the geographical separation is as little as 160 mi (257 km) and even closer along the Rio Grande (50 mi; 80 km). The closer proximity of western and eastern yellow-billed cuckoos in this region may be caused in part by the lower height of the mountain range being a less effective barrier (Hubbard 1978, p. 32; Howe 1986, p. 2). Historically, this gap was wider, because the banks of the Pecos River did not have riparian woodland and the area was not used by the species. Today, the riverine habitat along the Pecos River consists primarily of introduced tamarisk (
Tamarix
spp.), and it is thought that yellow-billed cuckoos from eastern North America have colonized the Pecos River system. Much of the area between the Pecos River and the Rio Grande in New Mexico and Texas consists of internal ephemeral drainages that are not connected to any major river systems and have no riparian habitat. Considering these factors along with the information on physical factors, we have included Texas west of the Rio Grande-Pecos River watershed boundary within the range of the western population. This physical division coincides with behavioral differences between eastern and western yellow-billed cuckoos, as discussed below.

South of the United States-Mexico border, yellow-billed cuckoos are separated by extensive areas of desert that lack suitable nesting and foraging habitat. In Mexico, the Chihuahuan Desert widens to 350 mi (563 km), and includes nearly all of the States of Chihuahua and Coahuila. There are very few records of yellow-billed cuckoos for this region, and we are not aware of any nesting records for either State. Suitable breeding habitat or connective riparian corridors are also lacking. Published range maps for the species do not include the eastern three-quarters of Chihuahua or the western three-quarters of Coahuila as part of the species' breeding range (Howell and Webb 1995, p. 347; Hughes 1999, p. 1). There are only 12 records of yellow-billed cuckoos from Chihuahua: 11 specimens from the 1940s to 1960, and a sight observation in 2003. There are only nine records of the species from Coahuila: six specimen and three sight records (1958, 1988, and 2011). Three of the specimens from Coahuila were identified as eastern yellow-billed cuckoos on their museum records, and the others were not identified to subspecies. Seven specimens from Chihuahua were identified to subspecies and six of these were considered the western subspecies. It is likely that many, if not most, of the records from this region are of migrating yellow-billed cuckoos, as 16 are from May to mid-June or from late September, and only 5 are from late June or July, the primary breeding season.

From this information we concluded that the Chihuahua-Coahuila border was the most biologically supportable boundary for the population segment. The boundary then follows the southern border of Chihuahua west to the Continental Divide, then south along the divide through the State of Durango and west along the southern border of Durango and Sinaloa. There are no breeding season records for yellow-billed cuckoos from the State of Nayarit or Jalisco or farther south along the

Pacific coast of Mexico. The species has occurred sporadically in the State of Zacatecas, but the records are from east of the Continental Divide.

Eastern and western yellow-billed cuckoos are highly migratory, and the two populations may spend winters in overlapping regions in South America. However, we do not have information to indicate that there is anything more than an extremely low level of interchange (if any at all) between the two populations during the breeding season. This conclusion is supported by differences in habitat use and morphology, which are genetically controlled traits, as discussed in the following sections.

Although the Rocky Mountains and the Chihuahuan Desert may not wholly prevent movement of yellow-billed cuckoos between the east and west, especially in a migratory species that winters far to the south, and moves thousands of miles between its wintering and breeding grounds, the available information indicates that this mountain range and desert substantially separates yellow-billed cuckoo populations during the breeding season, thereby effectively separating them into discrete populations. The separation between yellow-billed cuckoo population segments in the east and west is a physical one that is maintained by their behavioral differences, which we discuss below.

Behavioral Discreteness

Data collected from publications and other sources demonstrate the existence of behavioral differences between yellow-billed cuckoos in the east and west.

Yellow-billed cuckoo populations in the east and west differ in the timing of arrival on the breeding grounds in the spring. Yellow-billed cuckoos in western North America arrive on the breeding grounds 4 to 8 weeks later than eastern yellow-billed cuckoos at similar latitude (Franzreb and Laymon 1993, pp. 24-25; Hughes 1999, pp. 5-6, 12-13; Laymon 2000,
in. litt.,
pp. 15-16). Timing of spring migration and arrival on the breeding grounds has been determined to be the result of an evolved response under genetic control, and is likely caused by east-west climatic, habitat, and food availability differences (Cresswell
et al.
2011, pp. 13-15; Pulido
et al.
2001). The watershed boundary between the Rio Grande and the Pecos Rivers also appears to separate yellow-billed cuckoos that arrive in spring migration earlier on the Pecos River and those that arrive later on the Rio Grande in addition to separating morphological differences.

Information, including timing of migration, indicates that yellow-billed cuckoos from Texas west of the Pecos River (from the Rio Grande upstream of Big Bend) and from northwestern Mexico (Chihuahua, Sonora, Sinaloa, Durango, Baja California Sur) exhibit greater similarity to yellow-billed cuckoos in western North America, and those on the Pecos River in Texas and eastern Mexico (Coahuila, Nuevo Leon, Tamaulipas, San Luis Potosi) are more similar to yellow-billed cuckoos in the east (Wauer 1971, p. 96; Oberholser and Kincaid 1974, pp. 434-435; Franzreb and Laymon 1993, pp. 17-28; Hughes 2000,
in litt.
pp. 1-2, 26; Sproul 2000,
in litt.,
pp. 1-5). Based on the best available science, the watershed boundary between the Rio Grande and Pecos Rivers is the optimum dividing line between eastern and western yellow-billed cuckoo in this area.

Based on migration timing, yellow-billed cuckoos split into two populations. This split occurs along the line that corresponds with the traditional subspecies boundary (see Figure 1, above).

Discreteness Conclusion

The available information indicates that the yellow-billed cuckoo population segment that occurs west of the Continental Divide (as defined above) in the United States, in southwestern Canada, and in northwestern Mexico is markedly separated from the eastern population segment of yellow-billed cuckoo, including those that nest in eastern North America, eastern Mexico, certain Caribbean Islands, and the Yucatan Peninsula. The distribution of the western populations is markedly separated physically (geographically) during the breeding season from the distribution of other yellow-billed cuckoo populations by high mountains, extensive desert, or nonhabitat areas with the shortest geographical separation occurring across 160 mi (257 km) of desert between the Pecos River and Rio Grande in southern New Mexico and western Texas with the exception of nesting of western yellow-billed cuckoos near Big Bend National Park in Texas. Evidence that this geographical separation between populations has been consistent through time may be found in the differences in the two populations' biology and morphology. Even in this area of closest proximity, information on genetically controlled behavior available in the scientific literature provides evidence of a biological separation between the western populations and eastern populations.

Under our DPS policy, the standard for discreteness does not require absolute separation because this can rarely be demonstrated for any population of organism. For the yellow-billed cuckoo populations in western North America, we have met this standard, and, therefore, we consider the western population segment of the yellow-billed cuckoo from southern British Columbia, Canada south along the Continental Divide (including the Rio Grande basin) in the United States into Mexico, and ending at the coast in the State of Sinaloa, Mexico, to be discrete per our DPS policy. We conclude that the western population segment of the yellow-billed cuckoo is discrete from the remainder of the species because the yellow-billed cuckoo population segment that nests west of the Continental Divide (as defined above) and in northwestern Mexico is markedly separated geographically and behaviorally from all other populations of yellow-billed cuckoo, including those that nest in eastern North America.

Significance

Under our DPS policy, once we have determined that a population segment is discrete, we consider its biological and ecological significance to the larger taxon to which it belongs. Our DPS policy provides several potential considerations that may demonstrate the significance of a population segment to the remainder of its taxon, including: (1) Evidence of the persistence of the discrete population segment in an ecological setting unusual or unique for the taxon, (2) evidence that loss of the discrete population segment would result in a significant gap in the range of the taxon, (3) evidence that the population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range, or (4) evidence that the discrete population segment differs markedly from the remainder of the species in its genetic characteristics.

We have found substantial evidence that two of these four significance criteria (numbers 2 and 4) are met by the discrete population segment of yellow-billed cuckoos that occurs west of the Continental Divide (as defined above). We address these significance factors below as they relate to the population segment of western yellow-billed cuckoo. We focus on whether the loss of this population segment would result in a significant gap in the range of the taxon and evidence that the discrete

population segment differs from other population segments in its genetic characteristics in demonstrating significance of the DPS.

Evidence That Loss of the Discrete Population Segment Would Result in a Significant Gap in the Range of the Taxon

Loss of the discrete population segment would result in a significant gap in the range of the taxon because an extensive area would be without yellow-billed cuckoos if the western population segment were lost. Seven entire States and substantial portions of five additional States in the United States, and six States in Mexico, that are currently occupied would have no breeding populations of the species. Bird migration experts divide the North American continent into four migratory flyways: The Atlantic, Mississippi, Central, and Pacific. The range of the yellow-billed cuckoo west of the Rocky Mountains covers the entire Pacific flyway and half of the Central flyway. Additionally, the range of the yellow-billed cuckoo west of the Rocky Mountains covers 1,350,000 square (sq) mi (3,496,500 sq km), or approximately 40 percent of the lower 48 States. Even though the actual area occupied by the species in western North America is less than the total area identified above, the potential loss of the western population of the yellow-billed cuckoo would constitute a significant gap in the range of the species in North America.

Evidence That the Discrete Population Segment Differs Markedly From Other Populations of the Species in Its Genetic Characteristics

Data collected from publications and other sources demonstrate the existence of morphological and physiological differences between yellow-billed cuckoos in the east and west. Morphologically, the yellow-billed cuckoos in western North America are generally larger, with significantly longer wings, longer tails, and longer and deeper bills (Franzreb and Laymon 1993, p. 25). Banks, in a review of the species taxonomic status (1988, pp. 473-477), grouped yellow-billed cuckoo specimens into 19 regional groups, 7 in the western United States and western Mexico, 10 in the eastern United States and eastern Mexico, 1 in New Mexico, and 1 in the Caribbean. He found yellow-billed cuckoos in the east to be uniform in measurement throughout their range and yellow-billed cuckoos in the west to be uniform in measurements throughout their range (Banks 1988, p. 475). Banks stated that the change from smaller to larger yellow-billed cuckoos appeared to take place in extreme western New Mexico or extreme eastern Arizona (Banks 1988, p. 476). A subsequent analysis, based on available specimens from New Mexico and western Texas, showed the watershed boundary between the Pecos River and the Rio Grande as the apparent boundary between the smaller eastern and larger western birds, with a majority of yellow-billed cuckoos on the Rio Grande above Big Bend being larger western birds (63 percent, n=19) and the majority of yellow-billed cuckoos on the Pecos River being smaller eastern birds (82 percent, n=11) (Franzreb and Laymon 1993, p. 25). This is the only area where the ranges of the western and eastern population segments are in close proximity; elsewhere the two populations are separated by wide expanses of unsuitable, unoccupied habitat (see Figure 1, above).

One peer reviewer measured 35 cuckoos from the Rio Grande and 25 cuckoos from the Pecos River in the field. With the exception of wing and tail measurements, accurate measurements are hard, if not impossible, to obtain from live birds under field conditions. Male and female cuckoos averaged longer wings and tails on Rio Grande than on the Pecos River, with the difference being more pronounced on male than on female cuckoos. Sample sizes were insufficient to do t-tests to compare the means for the wing and tail data. The bill measurements that the reviewer took in the field were not reliable and therefore could not be compared, and as a result the comparison using the Discriminant Function equations developed by Franzreb and Laymon (1993, pp. 17-28) could not be used reliably on the data.

Other physical and morphological differences exist between yellow-billed cuckoos in the east and west, and provide additional evidence of ecological significance. These include:

• Yellow-billed cuckoos in western North America produce larger eggs (1.2 percent longer, 0.6 percent wider, and 3.2 percent heavier) with thicker eggshells (7.1 percent thicker) (Hughes 1999, p. 14), which is an evolved trait that would help yellow-billed cuckoos in the west to cope with potential higher egg water loss in the hotter, drier conditions of western North America (Hamilton and Hamilton 1965, pp. 426-430; Ar
et al.
1974, pp. 153-158; Rahn and Ar 1974, pp. 147-152).

• Juvenile yellow-billed cuckoos in the east have yellow bills (Oberholser and Kincaid 1974, pp. 434-435), while juvenile yellow-billed cuckoos in the west have all-black bills (Franzreb and Laymon 1993, p. 26).

• Adult yellow-billed cuckoos in the west have a lower mandible that is orange-yellow, while yellow-billed cuckoos in the east have lower mandibles that are bright yellow (Franzreb and Laymon 1993, p. 26; Laymon 2000,
in litt.,
p. 14).

• As noted previously, adult yellow-billed cuckoos in the west are larger and heavier, on average, than adult yellow-billed cuckoos in the east. More than 80 percent of individuals can be assigned to east or west based on morphological measurements (see also Oberholser and Kincaid 1974, pp. 434-435; Banks 1988, pp. 473-477; 1990, p. 538; Franzreb and Laymon 1993, pp. 17-28). The size differences between eastern and western cuckoos are discussed in detail in the
Taxonomy
section of the proposed rule (78 FR 61624-61625; October 3, 2013).

Information, including morphology, indicates that yellow-billed cuckoos from Texas west of the Pecos River (from the Rio Grande upstream of Big Bend) and from northwestern Mexico (Chihuahua, Sonora, Sinaloa, Durango, Baja California Sur) exhibit greater similarity to yellow-billed cuckoos in western North America, and those on the Pecos River in Texas and eastern Mexico (Coahuila, Nuevo Leon, Tamaulipas, San Luis Potosi) are more similar to yellow-billed cuckoos in the east (Wauer 1971, p. 96; Oberholser and Kincaid 1974, pp. 434-435; Franzreb and Laymon 1993, pp. 17-28; Hughes 2000,
in litt.
pp. 1-2, 26; Sproul 2000,
in litt.,
pp. 1-5). Based on the best available science, the watershed boundary between the Rio Grande and Pecos Rivers is the optimum dividing line between eastern and western yellow-billed cuckoo in this area.

Based on morphological measurements, bill color of young and adults, egg size and weight, and migration timing, yellow-billed cuckoos split into two populations. This split occurs along the line that corresponds with the traditional subspecies boundary (see Figure 1, above). Phenotypically or outwardly expressed traits present substantial evidence that the western population segment of yellow-billed cuckoo differs markedly from other populations of the species.

However, the strongest evidence of differences between yellow-billed cuckoos in the western population segment and those of the east in genetic characteristics is the difference in timing of migrations. This difference can only have developed as an evolved trait in response to environmental factors over a long period of time, and thus is genetically linked (Cresswell
et al.
2011, pp. 13-15; Pulido
et al.
2001). As previously discussed, the difference

in size of yellow-billed cuckoos between east and west, as well as differences in size, weight, and shell thickness of eggs, are also evolved genetically linked traits. As discussed in the October 3, 2013, proposed rule, researchers have developed methods using these phenotypic (outwardly expressed) traits that correctly predicted separation for nearly 90 percent of yellow-billed cuckoos that were eastern, and up to approximately 86 percent that were western (Franzreb and Laymon 1993, pp. 17-28). Thus, based on the phenotypic traits, there is indirect evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.

Significance Conclusion

The best available information indicates that the discrete yellow-billed cuckoo population segment that nests west of the Continental Divide (as defined above) and in northwestern Mexico is important to the taxon to which it belongs because: (1) Loss of the population segment would leave a significant gap in the species' range (more than one third of the species' range would be vacant); and (2) it differs markedly from other yellow-billed cuckoo populations in morphology (e.g., western yellow-billed cuckoos are larger) Therefore, we conclude that the western population segment of the yellow-billed cuckoo is
significant
per our DPS Policy.

DPS Conclusion

Based on the best scientific and commercial data available on distribution as well as behavioral and morphological characteristics of the species, we have determined that the western population segment of the yellow-billed cuckoo is both discrete and significant per our DPS policy. Therefore, we conclude that the western distinct population segment of the yellow-billed cuckoo is a DPS, and thus a “species” under section 3(16) of the Act. Our determination of biological and ecological significance is appropriate because the population segment has a geographical distribution that is biologically meaningful.

The term “distinct population segment” is not commonly used in scientific discourse. As such, and in contrast to taxonomically defined species and subspecies, there is no established name for the western distinct population segment of the yellow-billed cuckoo in the available literature; we will refer to this “species” (DPS) as the western yellow-billed cuckoo. The range of the western yellow-billed cuckoo in Canada includes the area of Vancouver Island and along the Fraser River system upstream to Kamloops to the Rocky Mountains west of the Continental Divide. In the United States the DPS includes the area west of the Continental Divide, south through Montana, Wyoming, Colorado, and along the watershed divide between the upper and middle Rio Grande and Pecos Rivers in New Mexico and Texas, south to Big Bend in southwestern Texas, and extending to the States of the west coast. In Mexico, the DPS is the area west of the eastern and southern border of the State of Chihuahua, west of the Continental Divide in the State of Durango, and the southern border of the State of Sinaloa (Figure 2).

ER03OC14.005

Summary of Comments and Recommendations

In the proposed rule published on October 3, 2013 (78 FR 61621), we requested that all interested parties submit written comments on the proposal by December 2, 2013. The comment period was reopened on December 26, 2013, and remained open until February 24, 2014 (78 FR 78321). The comment period was reopened again on April 10, 2014, and remained open until April 25, 2014 (79 FR 19860). We also contacted appropriate Federal and State agencies, scientific experts and organizations, and other interested parties and invited them to comment on the proposal. Newspaper notices inviting general public comment were published in the Idaho State Journal (Pocatello, ID), Post Register (Idaho Falls, ID), Idaho Mountain Express (Sun Valley, ID), Idaho Statesman (Boise, ID), Coeur d'Alene Press (Coeur d'Alene, ID), Las Vegas Sun (Las Vegas, NV), Las Vegas Review-Journal (Las Vegas, NV), Reno Gazette-Journal (Reno, NV), The Oregonian (Portland, OR), Yakama Herald, (Yakima, WA), Wenatchee World (Wenatchee, WA), The Olympian (Olympia, WA), The Spokesman Review (Spokane, CA), Bellingham Herald (Bellingham, WA), Salt Lake Tribune (Salt Lake City, UT), Helena Independent Record (Helena, MT), The Missoulian (Missoula, MT), Valley Courier (Alamosa, CO), Craig Daily Press (Craig, CO), (The Daily Sentinel (Grand Junction, CO), El Paso Times (El Paso, TX), Albuquerque Journal (Albuquerque, NM), The Arizona Republic (Phoenix, AZ), The Californian (Bakersfield, CA), and Press-Enterprise (Riverside, CA). We did not receive any requests for a public hearing.

During the comment periods for the proposed rule, we received 34,459 comment letters directly addressing the proposed listing of the western DPS of the yellow-billed cuckoo as a threatened species. The vast majority of these comment letters voiced their support or opposition to the action, but did not provide significant supporting information on the proposed listing. A total of 34,380 letters were in support of the listing, while 54 letters were in opposition to listing, with 25 commenters providing additional information, but took no position on the listing of the species. Approximately 141 of these comment letters provide additional information or comments. All substantive information provided during comment periods has either been incorporated directly into this final determination or is addressed below.

Peer Review

In accordance with our peer review policy published on July 1, 1994 (59 FR 34270), we solicited expert opinion from five knowledgeable individuals with scientific expertise that included familiarity with the yellow-billed cuckoo and its habitat, biological needs, and threats. We received responses from all five of the peer reviewers.

We reviewed all comments we received from the peer reviewers for substantive issues and new information regarding the listing of the western DPS of the yellow-billed cuckoo. The peer reviewers generally concurred with our methods and conclusions, and provided additional information, clarifications, and suggestions to improve the final

rule. Peer reviewer comments are addressed in the following summary and incorporated into the final rule as appropriate.

Peer Reviewer Comments

(1)
Comment:
One reviewer discussed the heritability of migration timing, indicating that the difference in migration timing between eastern and western cuckoos is reflective of genetic differences and added a supportive reference (Pulido
et al.
2001).

Our Response:
In the proposed and this final rule, we outlined our reasoning for determining that the western populations of the yellow-billed cuckoo constitute a valid DPS (see
Distinct Vertebrate Population Segment Analysis
, above). In our determination, we relied on behavioral and morphological and other characteristics of the species to support separation and distinctness from yellow-billed cuckoos in the east. Although genetics most likely play a role in behavioral and morphological aspects of a species, in our determination we did not rely on specific genetic information or separation to come to our conclusion. The views of the peer reviewer and the information they provided (Pulido
et al.
2001, pp. 149-158) further support our conclusions reached in determining a valid DPS for the western yellow-billed cuckoo. We revised this final rule to include the information provided.

(2)
Comment:
One reviewer stated that a close examination of the DNA studies conducted on cuckoos to date would infer a deeper genetic divergence between western and eastern cuckoos than presented in the proposed rule and that further analysis would likely support division of species into two subspecies. The reviewer also provided a critique of the techniques used in the studies to date, noting that markers used in all three genetics studies evolve too slowly to reveal genetic structure within the species, and that the choice of outgroup for study comparison was flawed in one study.

Our Response:
See response to
Comment
1 above for a discussion of how we used genetic information in our DPS determination. Although we agree that further studies and information on the genetics for the yellow-billed would assist in further validating our determination of separation between eastern and western yellow-billed cuckoo populations, we must rely on the best scientific or commercial data available to make our listing determinations. We appreciate the information provided and have made some revisions to the DPS analysis to incorporate citations provided by the peer reviewer, as needed.

(3)
Comment:
Two reviewers indicated that recent research has shown that vocalizations cannot be reliably used to determine the sex of cuckoos in the field. Two public commenters also raised this concern.

Our Response:
We concur and have revised the text to clarify information on vocalizations for the western yellow-billed cuckoo.

(4)
Comment:
One reviewer indicated that the habitat section could be strengthened by presenting habitat models that have been developed. This reviewer suggested that the presentation of tamarisk as a habitat component could be improved by using information from several references from research on the Colorado River (see Johnson
et al.
2008a, Johnson
et al.
2012, McNeil
et al.
2012). Within-patch vegetation measurements show that sites occupied by western yellow-billed cuckoos do not include dense tamarisk patches.

Our Response:
Based on observations of western yellow-billed cuckoos, we have identified riparian trees including willow (
Salix
sp.), Fremont cottonwoods (
Populus fremontii
), alder (
Alnus
sp.), walnut (
Juglans
sp.), sycamore (
Platanus
sp.), boxelder (
Acer
sp.), ash (
Fraxinus
sp.), mesquite (
Prosopis
sp.), and tamarisk (
Tamarix
sp.) as habitat that provides cover, shelter, foraging, and dispersing habitat for the western yellow-billed cuckoo. Tamarisk is considered a nonnative, invasive species across the West. Although the western yellow-billed cuckoo uses tamarisk as a component of its habitat, it is usually in areas where the habitat has been degraded. We appreciate the peer reviewer's information on habitat modeling and will review this information in development of any final critical habitat determination for the species.

We have reviewed the information provided by the reviewer and have revised our discussion of habitat selection and tamarisk use and compatibility for the western yellow-billed cuckoo in this final rule (see “Use of Tamarisk by Western Yellow-billed Cuckoos and the Spread of the Introduced Tamarisk Leaf Beetle into the Southwest,” below).

(5)
Comment:
One reviewer suggested that estimates of breeding populations of western yellow-billed cuckoos may be overestimates and the numbers may be even lower than indicated in the proposed rule.

Our Response:
We are aware of the difficulties in obtaining accurate counts of western yellow-billed cuckoos. Survey methods for western yellow-billed cuckoos have evolved over time since the first play-back surveys were conducted in California in the 1970s. Some changes in survey method include changes in the distance between calling stations (100 vs. 200 meters), changes in the number of calls played at calling stations (5 vs. 10 calls), number of surveys carried out during the breeding season (2 to 5 surveys), and the timing of the surveys (1 June to 15 August vs. 15 June to 1 August). Despite these changes, general response rates have remained constant. On average, an individual western yellow-billed cuckoo will respond to playback call 50 percent of the time, and one member of a pair will respond 75 percent of the time. With a second visit, the probability of an individual responding has risen to 75 percent, and the probability of one member of a pair responding has risen to 94 percent. With three visits, the probability of an individual responding is 94 percent, and the probability of one member of a pair responding is 99.6 percent.

Obtaining accurate survey results are made more difficult because: (1) Western yellow-billed cuckoos often have helper males at the nest; (2) they are only loosely territorial; (3) nests of adjacent pairs can be very close to each other; (4) female western yellow-billed cuckoos often lay a second and third clutch sometimes with different mates; and (5) it is likely that they move from one river system to another between clutches. These unusual behaviors can lead to either an over count or an under count of individuals, pairs, or territories.

Many of the earlier population estimates were made of pairs of western yellow-billed cuckoos. For the reasons listed above, some recent researchers have decided that it is more accurate to use the term territories rather than pairs. An assessment of the methodology used to determine pairs in the older studies and territories in the more recent studies concludes that very similar methodology is used and that the numbers are comparable.

In some cases, we were able to use the original survey data and simply compare the number of survey hours and number of western yellow-billed cuckoos surveyed and compare them from one year to the next and one time period to another. This is a very reliable and accurate method of comparison. In other cases, such as that at the South Fork Kern River Valley in California from 1985 to 2001, when all nesting pairs were either documented by finding a nest or seeing positive nesting behavior (e.g., western yellow-billed cuckoos carrying food to young) the

number of pairs were compared over time.

We have taken all of these difficulties and changes of survey methods and changes of data and behavior interpretation into account in our assessment of survey results and western yellow-billed cuckoo population trends. We have used the best available data and science in determining population estimates and trends. Because we have been aware of the changes in survey methods and have factored that information into our analysis, we are confident that our estimates of breeding populations are accurate.

(6)
Comment:
One reviewer indicated that habitat use separates eastern and western cuckoos; observations suggest that in eastern New Mexico and Texas yellow-billed cuckoos from eastern populations nest in monotypic stands of tamarisk, while western yellow-billed cuckoos do not.

Our Response:
We have considered this information in our determination of the DPS for the yellow-billed cuckoo. Although credible observations of species behavior are valuable, peer-reviewed published materials would further support these observations, and additional research on this topic would be valuable. The information provided will be considered further in the development of the final critical habitat designation for the species and in recovery planning.

(7)
Comment:
Two reviewers suggested that the section on climate change could be condensed and that uncertainties in forecasting precipitation could bog down conservation actions that would clearly benefit western yellow-billed cuckoos in the near future.

Our Response:
The Service used the climate change information that was available in the literature. Because the western DPS of the yellow-billed cuckoo covers such a large area, the effects of climate change will be different in the various regions. The Pacific Northwest may become cooler and wetter, the desert Southwest may become warmer and dryer. The exact effect of these changes on western yellow-billed cuckoos is difficult to predict. However, based on our review of the literature, we have concluded that a warmer and dryer Southwest, an area that is already water-stressed, with a growing human population, is likely to have an adverse effect on riparian habitat. This will exacerbate the changes that have already occurred in the region and should not be ignored. We appreciate the expressed concerns; however, we have retained the information presented in the section.

(8)
Comment:
One reviewer provided survey results indicating that western yellow-billed cuckoos have been detected along the San Juan and Green rivers in Utah, although it is not yet known whether breeding occurs in these areas. The reviewer notes that further surveys are needed.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This information will also be considered in our final critical habitat designation.

(9)
Comment:
One reviewer commented that a potential planned activity is the reallocation of water from the San Juan River on Navajo Tribal lands, which could negatively affect water delivery on the Colorado River and western yellow-billed cuckoo habitat on the Lower Colorado River.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This information will also be useful in recovery planning and implementation.

(10)
Comment:
One reviewer provided information that describes the ecological cascade process that leads to loss of western yellow-billed cuckoo habitat in riparian areas. The peer reviewer stated that the key to sustaining western yellow-billed cuckoo habitat is maintaining an ongoing process of new land creation and flow patterns conducive to colonization of willow and cottonwood. The peer reviewer also noted that it is problematic that a National Wildlife Refuge (NWR) on Sacramento River only occurs on one side of the river, and the opposite bank is not allowed to erode.

Our Response:
We appreciate this additional information and have considered this in our listing determination. The information will be helpful when developing a recovery plan for the western yellow-billed cuckoo.

(11)
Comment:
One reviewer adds an additional pervasive threat is the design of open channel flood control channels with inappropriately smooth roughness coefficients. This over-scours the floodplains and requires removal of woody riparian vegetation that regenerates on floodplains. This leads to floodplains with no western yellow-billed cuckoo habitat.

Our Response:
We have added this information to section “Encroachment of Levees and Flood Control and Bank Stabilization Structures into the River Channel and Floodplain” in the Factor A discussion in this final rule.

(12)
Comment:
One reviewer provides information on several additional projects that he indicates are impacting western yellow-billed cuckoo habitat. The reviewer notes that the U.S. Army Corps of Engineers (USACE) Sacramento River Bank Protection Project has been channelizing and rip-rapping river banks for many decades and that the project impedes the dynamic riverine processes that create western yellow-billed cuckoo habitat. The reviewer adds that the California Department of Water Resources has proposed a new reservoir project (the Sites Reservoir) for off-stream water storage, suggesting that the project would be a major water diversion project that would further degrade stream power on the Sacramento River, and contribute to an ecological cascade on the river (see
Comment
10 above and the discussion under Factor A below). The reviewer also noted two proposed projects that he thinks would provide a potential conservation benefit to western yellow-billed cuckoo habitat. Both projects involve the creation of several miles-long oxbow lakes on the Sacramento River, at Woodson Bridge, and at a pumping facility across from Llano Seco unit of Sacramento River NWR.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This information will be helpful in developing and implementing the recovery plan for the species.

(13)
Comment:
One reviewer indicated that in Conservation Efforts section under the Factor E discussion, a distinction should be made between “active” restoration and “process-based” restoration.

Our Response:
We have revised the text in the section to clarify the difference in types of restoration activities.

(14)
Comment:
One reviewer measured 35 cuckoos from the Rio Grande and 25 cuckoos from the Pecos River. He found that Rio Grande males and females were larger for all measurements than Pecos cuckoos, but Pecos cuckoos are larger than eastern or Trans Pecos cuckoos reported in Franzreb and Laymon's (1993, pp. 17-28) subspecies paper. He applied the Discriminant Function Analysis (DFA) equation (developed by Franzreb and Laymon, 1993, pp. 17-28) to 35 cuckoos from Rio Grande, of which 86 percent tested as western and 25 cuckoos from Pecos River of which 68 percent tested as western.

Our Response:
We thank the reviewer for this information. However, we are concerned that the measurements may have been taken incorrectly for the

following reasons. We first note that, with the exception of wing measurements, accurate measurements are hard, if not impossible, to obtain from live birds under field conditions. We are concerned that in the given sample, bill-depth measurements may have been measured incorrectly because all individuals measured, regardless of area of origin, had deeper bills than any of the cuckoos measured by Banks (1988, pp. 473-477) or Franzreb and Laymon (1993, pp. 17-28). It is likely that these measurements were taken on an incorrect location on the bill. We note that several of the bill-length measurements reported were also record lengths for cuckoos, regardless of origin and suspect that they too were likely measured incorrectly. The use of these incorrect measurements in the DFA equations would be expected to yield incorrect “likely area of origin.” Therefore, we have not used this information in our final listing determination.

Federal Agency Comments

During the development of the proposed and this final listing rule, we coordinated with Federal agencies and asked for their input on the information presented and any concerns they may have. We have not included specific comments and responses to Department of the Interior (DOI) agencies in this rule (Bureau of Land Management, Bureau of Reclamation, and National Park Service). We have worked with the DOI agencies during the development of this rule, and their comments and concerns are included in the record materials for this final determination. We have reviewed any DOI comments and information, and have made changes that we determined were appropriate to the final listing of the western yellow-billed cuckoo. A total of seven comment letters were received from five Federal agencies from outside the DOI, and they are outlined below.

(15)
Comment:
The U.S. Air Force stated that training flights from Luke Air Force Base (AFB) may pass over western yellow-billed cuckoo habitat, but they are unlikely to disturb the western yellow-billed cuckoos because the airplanes fly over 500 ft. above ground level, while western yellow-billed cuckoo fly, forage, and nest within the canopy of the trees. Also, the duration of the sound from the jet airplanes is only for a few seconds and the flights are infrequent.

Our Response:
We appreciate receiving the information on Air Force training flights at Luke AFB. We will consider this information during any consultation regarding the species in the future.

(16)
Comment:
The USACE provided references that deal with southwestern willow flycatcher (
Empidonax traillii extimus
) consultations and management at Lake Isabella, California. They stated that their conservation plan and associated conservation easements for southwestern willow flycatchers provide habitat protections for the western yellow-billed cuckoo as well as least Bell's vireos (
Vireo bellii pusillus
). They are concerned that if the western yellow-billed cuckoo is listed and formal consultation for long-term operations of Isabella Reservoir are triggered, the USACE may be required to “reoperate” the reservoir, which would increase risk of loss of human life and cause significant impacts to economics downstream. This concern was also voiced by one public commenter.

Our Response:
Although specific project activities may require additional review and potentially result in formal consultation for various Federal actions, it is reasonable to assume that the conservation plan and associated conservation easements for the southwestern willow flycatcher may provide habitat protections for the western yellow-billed cuckoo. However, consultation with the Service will not likely result in operation decisions that would cause a risk of loss of human life or cause significant impacts to downstream economies. We have been coordinating with the USACE on their activities and dam operation at Lake Isabella as it relates to all listed species and will continue to do so into the future.

(17)
Comment:
The U.S. Forest Service (USFS) provided several reports on western yellow-billed cuckoo surveys conducted at Isabella Reservoir. The Southwest Region of the USFS does not think they have western yellow-billed cuckoos on the Carson or Cibola National Forests. They also had several questions about wording in the proposed rule regarding grazing and listed several references regarding the effects of well-managed grazing, which they say has less adverse impact on western yellow-billed cuckoos and their habitat than traditional, poorly managed grazing. Lastly, they stated that mesquite bosque habitat was very important to western yellow-billed cuckoos and that the habitat was more important than the proposed rule indicated.

Our Response:
We appreciate the additional information provided by the USFS and have considered it or incorporated changes to language into our final listing determination. Well-controlled grazing activity can be compatible within riparian zones and in western yellow-billed cuckoo habitat depending on the conservation measures implemented for the grazing activity. The amount of management depends on the sensitivity of the habitat at any given location and would most likely need to be managed on a site-by-site basis. For example, a grazing regime used on Audubon California's Kern River Preserve in the South Fork Kern River Valley limits grazing to outside the growing season (October to March). This time restriction allows for regeneration of willows and cottonwoods and precludes the tree browsing and high-lining that often accompanies heavy summer (growing season) grazing. We concur that mesquite bosque habitat is very important to western yellow-billed cuckoos, and this has been stated clearly in the proposed and this final rule.

(18)
Comment:
The U.S. Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) in Texas stated that they are interested in helping landowners conserve and manage critical habitat for the western yellow-billed cuckoo.

Our Response:
We appreciate this additional information and have considered this in our listing determination. NRCS' cooperation and assistance will be very helpful during the recovery phase for the species.

(19)
Comment:
The International Boundary and Water Commission provided information on riparian habitat restoration along the Rio Grande as well as results of recent western yellow-billed cuckoo surveys.

Our Response:
We appreciate this additional information and have considered this in our listing determination. Restoration of riparian habitat will be an important phase in the recovery of the western yellow-billed cuckoo. This information will also be helpful in the development and implementation of a recovery plan for the western yellow-billed cuckoo.

(20)
Comment:
The USDA NRCS in Texas expressed concern regarding economic impacts to local landowners and municipalities. This concern was echoed by several public commenters.

Our Response:
According to section 4(b)(1)A) of the Act, we are to base our listing determinations solely on the basis of the best scientific and commercial data available as they relate to the five factors listed in section 4(a)(1) of the Act. The consideration of economics is only related to the designation of critical habitat under section 4(b)(2) of the Act.

Comments From States

Section 4(i) of the Act states, “the Secretary shall submit to the State agency a written justification for his failure to adopt regulations consistent with the agency's comments or petition.” Comments received from the States regarding the proposal to list as a “threatened species” for the western DPS of the yellow-billed cuckoo are addressed below. We received 17 comment letters from 17 State agencies in 11 States. Of the 17 letters submitted, 9 were from State wildlife agencies. We did not receive comments from the State of Oregon.

Washington State

(21)
Comment:
The Washington State Department of Fish and Wildlife supports the DPS determination and listing of the western yellow-billed cuckoo as threatened. This is based on their observations that reports of individual occurrences for the State have been very rare for the past several decades and that the species is not confirmed to be breeding in the State. This is despite having some sizable areas of riparian habitat still remaining along the Lower Columbia River and additional habitat improvements, acquisition, and restoration efforts elsewhere in the State. The Washington State Department of Fish and Wildlife provided suggestions for clarification of habitat use by the western yellow-billed cuckoo in moist riparian habitat areas of western Oregon, western Washington, and southwestern British Columbia. They also provided information on several records of wider habitat use in the Northwest and suggested that there is historical evidence that the species may have used conifer woodlands and open brushy hillsides in Washington as secondary nesting habitat (Bent 1940, pp. 54-70; Jewett
et al.
1953, pp. 342-343).

Our Response:
We appreciate this additional information and have considered this in our final listing determination. This habitat information has been discussed in detail in our proposed critical habitat designation. See the proposed critical habitat rule for the western yellow-billed cuckoo published in the
Federal Register
on August 15, 2014 (79 FR 48547). Also see the
Summary of Changes from Proposed Rule
section of this final rule and the
Habitat Use and Needs
section from the proposed listing rule for additional discussion on habitat use in Washington and Oregon (78 FR 61633-61634; October 3, 2013).

(22)
Comment:
The Washington State Department of Natural Resources (DNR) stated that they have developed a conservation strategy on its trust lands for conservation of salmonid freshwater stream habitat and other riparian obligate species habitat (DNR Trust Lands Habitat Conservation Plan). DNR stated that they would expect that implementation of the plan would assist in benefiting the western yellow-billed cuckoo's habitat and any future recovery efforts for the species. DNR also stated that they would continue to participate in the development of any future critical habitat designation.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This information will also be considered in our final critical habitat designation.

Idaho

(23)
Comment:
The Idaho Office of Species Conservation and the Idaho Department of Fish and Game stated that the Service fails to define foreseeable future in the proposed rule. This comment was echoed by several other commenters.

Our Response:
The Act does not specifically define the term “foreseeable future,” and does not require the Service to quantify the time period of foreseeable future in making listing determinations. The Solicitor for the Department of the Interior conducted a review of the Congressional intent behind the term “foreseeable future” in the Act, and concluded that Congress intended the term “foreseeable future” to describe the extent to which the Secretary can reasonably rely on predictions about the future in making determinations about the future conservation status of the species. The Secretary's ability to make reliable predictions may vary according to the threat at issue; consequently, the Solicitor concludes that this timeframe of “the foreseeable future is not necessarily reducible to a particular number of years. Rather, it relates to the predictability of the impact or outcome for the specific species in question.” In addition, the opinion notes that “definitive quantification is rarely possible . . . and not required for a `foreseeable future' analysis” (Department of the Interior Memorandum M-37021, January 16, 2009; available at:
http://www.doi.gov/solicitor/opinions/M-37021.pdf
).

In considering the foreseeable future as it relates to the status of the western yellow-billed cuckoo, we considered the factors acting on the species and looked to see if reliable predictions about the status of the species in response to those factors could be drawn. We considered the historical data to identify any relevant existing trends that might allow for reliable prediction of the future conservation status of the species (in the form of extrapolating the trends). We also considered whether we could reliably predict any future events that might affect the status of the species, recognizing that our ability to make reliable predictions into the future is limited by the variable quantity and quality of available data. Available population information for western yellow-billed cuckoo is limited for determining trends because no long-term rangewide status survey has been completed and the threats facing the species are variable in intensity and scope across the species' range and do not reliably provide a sound basis for specific timeframe predictions. The available data do not allow us to determine a specific timeframe for the foreseeable future for the western yellow-billed cuckoo; therefore, we rely on a qualitative assessment of the foreseeable future, in terms of that period of time over which we can reasonably predict the future population trends and threats to the species, and the likely consequences of those threats and trends for the status of the species. We have discussed the timeframe for when we have determined the threats are acting on the species under each factor in the
Summary of Factors Affecting the Species
and in our
Determination
sections below.

Montana

(24)
Comment:
Montana Fish, Wildlife, and Parks indicated that the portion of the State that is shown as being within the DPS has historically not been considered within the range of the species. The agency indicated that there are only 8 records for western Montana, and only 3 of those were found in the past 30 years. They stated that the western quarter of the State, west of the Continental Divide, should be excluded from the DPS and the species not listed in Montana. This comment was also echoed by commenters in Utah, Colorado, and Wyoming who wanted their States removed from the DPS.

Our Response:
We are aware of the limited number of sightings for the species in western Montana and other areas within the DPS. However, we consider yellow-billed cuckoos that are found in the portion of Montana west of the Continental Divide are western yellow-billed cuckoos based on dispersal and migratory patterns, the large gap between this region and southeastern Montana where eastern yellow-billed cuckoos sporadically

occur, and criteria used to map the DPS boundary. We based our boundary for the DPS on watershed boundaries along the upper elevation areas along the Rocky Mountains and on species occurrence records. It would be inconsistent and arbitrary to move the boundary or not include the western yellow-billed cuckoos in western Montana from the DPS regardless of how seldom they are found in the area.

Wyoming

(25)
Comment:
The Wyoming Game and Fish Department (WGFD) provided information on additional surveys for the Green River and on the State's classification of the species as a Tier III Species of Greatest Conservation Need with unknown population status and trends due to an extremely limited number of detections during targeted survey work (WGFD 2010, pp. IV-i-8). The WGFD stated it does not differentiate between eastern and western yellow-billed cuckoos but that habitat for the species continues to decline primarily as a result of nonnative plant (tamarisk) invasion. The WGFD believes that the estimate in the proposed rule of five or fewer pairs is an overestimate for the State, that it is highly unlikely that western yellow-billed cuckoos breed in the State on a consistent basis, and they doubt that the small numbers in Wyoming add to population viability of the subspecies. The WGFD recommended not designating any critical habitat or land use restrictions for the species in the State as most of the potential habitat for the species is above 7,000 ft (2,134 meters (m)). The State also recommended that ongoing and planned tamarisk removal should not be impeded as a result of the Service's final determination.

Our Response:
As stated in the proposed rule and this final rule, we agree that the number of western yellow-billed cuckoos nesting in Wyoming is small. It is also possible that western yellow-billed cuckoos do not nest in the State every year. However, the species most likely uses the available habitat as movement corridors or stop-over areas during its migration to areas farther north or as foraging areas during prey outbreaks. We will consider any information on critical habitat during the development of the final critical habitat designation. As a result of listing the species, we would expect agencies and organizations conducting tamarisk removal projects to do so in a manner compatible with conservation of the western yellow-billed cuckoo (see response to
Comment
28 below for additional information on tamarisk removal and the conservation of the western yellow-billed cuckoo).

California

(26)
Comment:
The California Department of Fish and Wildlife supports the DPS determination and listing of the western yellow-billed cuckoo as the species is already listed as endangered under the California Endangered Species Act (CESA) and the populations of the species in the State continue to decline. The California Department of Fish and Wildlife will continue to provide support in habitat management that will encourage recovery for the species in California.

Our Response:
We appreciate the review and support of the California Department of Fish and Wildlife. This information will help with the development and implementation of the recovery plan for the western yellow-billed cuckoo.

Nevada

(27)
Comment:
Nevada State Department of Wildlife concurred with the Service's concerns regarding declines of the western yellow-billed cuckoo and summarized the status of the species in the State. The Nevada State Department of Wildlife also provided clarifications and updated information on occurrence records and habitat for the State. The western yellow-billed cuckoo is a species of conservation priority in Nevada, and the Nevada State Department of Wildlife is dedicated to conserving the species and improving its habitat whether it is listed or not.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This information will also be used in the development of our final critical habitat designation and implementation of a recovery plan for the western yellow-billed cuckoo.

(28)
Comment:
Nevada State Department of Wildlife, Wyoming Game and Fish Department, Utah Office of Governor, and Colorado Department of Agriculture listed tamarisk invasion as a major threat for western yellow-billed cuckoos and their habitat. There is some concern that listing the western yellow-billed cuckoo will curtail tamarisk removal projects and riparian restoration. Several commenters would like us to develop a rule under section 4(d) of the Act for riparian habitat restoration.

Our Response:
The Service agrees that tamarisk is a major threat to the western yellow-billed cuckoo's habitat. We expect that in areas where restoration of native riparian vegetation is possible, removal of tamarisk would be considered a net benefit, as native riparian vegetation has a greater habitat value for the western yellow-billed cuckoo. If western yellow-billed cuckoos are documented to use an area slated for tamarisk removal, consultation with the Service may be necessary in order to jointly develop appropriate measures to avoid or minimize the potential for adverse effects to the western yellow-billed cuckoo. However, the process of listing a species as threatened under the Act is not designed to curtail projects that have the potential to benefit that species, and it is unlikely that beneficial tamarisk removal and riparian restoration projects would be negatively impacted from listing the western yellow-billed cuckoo. At this time, we are not developing a rule under section 4(d) of the Act for this species.

Utah

(29)
Comment:
The Director for the Utah Public Lands Policy Coordination Office stated that: (a) Utah has made great strides in conserving the yellow-billed cuckoo and its habitat and that the Service did not characterize the conservation benefits for the yellow-billed cuckoo as a State-sensitive species adequately in the proposed rule; (b) the DPS boundary is arbitrary and includes unoccupied areas or migratory habitat; and (c) the Service did not use or consider the best available scientific information provided by the Utah Division of Wildlife Resources (e.g., Beason 2009, additional Statewide surveys, GIS habitat models). The State requested that the Service not list the species as endangered or threatened under the Act, as it believes that the State is in the best position to manage and conserve the species and its habitat.

Our Response:
We commend the State of Utah on the efforts they have made in conserving the western yellow-billed cuckoo and its habitat. However, we were not supplied with any information by the State on specific conservation efforts for the western yellow-billed cuckoo, so characterization of the conservation benefits for the species is not possible.

We disagree that the DPS line is arbitrary. The DPS line used to separate the western yellow-billed cuckoo from yellow-billed cuckoos in the east in the vicinity of Utah was the watershed boundaries along the Continental Divide. This boundary does not imply that all areas within the DPS contain suitable habitat. In fact, most areas within the DPS do not contain suitable habitat for the species because the

species is restricted to riparian habitat and most of western United States is upland habitat covered by forest, desert, shrubland, or agriculture. Riparian habitat, by definition, is limited to the banks of rivers and streams, and comprises a very small percentage of the arid West. The DPS simply shows the outer limits that one can expect to find western yellow-billed cuckoos during the breeding season and during migration to breeding areas.

We received GIS data from the State of Utah and excel spreadsheets with location data apparently derived from surveys and incidental observation within the State. We did not receive the information mentioned in the comment letter (e.g., Beason 2009, additional statewide surveys, and GIS habitat models) from the State. During the development of this proposed rule and in response to the State's comment, we independently obtained a copy of the information cited (Beason 2009, pp. 1-19). The results of that study, which surveyed areas in and around Dinosaur National Park in Utah and Colorado, did not confirm any western yellow-billed cuckoo observations. We contacted the researcher and they confirmed the information.

Colorado

(30)
Comment:
The Colorado Department of Agriculture asked to participate in the recovery of the species and is actively removing tamarisk and Russian olive and restoring native riparian vegetation.

Our Response:
We appreciate this additional information and have considered this in our listing determination. This cooperation in recovering the species will be important in the development and implementation of a recovery plan for the species.

(31)
Comment:
The Water Resources Division of the Colorado Department of Natural Resources stated that riparian habitat is not threatened in Colorado and the western yellow-billed cuckoo should not be listed because adequate conservation efforts are underway.

Our Response:
Riparian systems in Colorado have been highly impacted by the nonnative, invasive tamarisk and Russian olive. Many of the other threats detailed in the proposed and this final rule also apply to riparian habitats in that State. In addition, the State of Colorado contains only a small portion of both the range and population of the western DPS of the yellow-billed cuckoo. Our obligation is to review and assess the population status as a whole and not on a regional or Statewide basis.

Arizona

(32)
Comment:
The Arizona Game and Fish Department supported the Service's overall determination of the western yellow-billed cuckoo as a DPS, but stated that using morphological information in the DPS significance section weakened the argument.

Our Response:
We appreciate this additional information and have considered this in our DPS analysis and listing determination. Morphological information is just one of the reasons we have determined that the western yellow-billed cuckoo is a valid DPS under our policy. In order to be more transparent in describing our rationale for our DPS determination, we included the morphological information as further evidence of the DPS. We conclude that including morphological information in the DPS
Significance
section helps to provide a complete picture of the differences between eastern and western yellow-billed cuckoos.

(33)
Comment:
The Arizona Game and Fish Department stated that they did not support listing the western yellow-billed cuckoo as it would be counterproductive to current conservation efforts.

Our Response:
Some restoration projects, especially where existing poor-quality, tamarisk-dominated habitat that is occupied by western yellow-billed cuckoo is being removed and higher quality, willow-cottonwood or mesquite habitat is being planted, may require consultation with the Service in order to jointly develop appropriate measures to avoid or minimize the potential for adverse effects to the western yellow-billed cuckoo. However, the process of listing a species as threatened under the Act is not designed to curtail projects that have the potential to benefit that species, and it is unlikely that beneficial tamarisk removal and riparian restoration projects would be negatively impacted from listing the western yellow-billed cuckoo. It is more likely that listing the western yellow-billed cuckoo will complement the recovery efforts and potentially provide additional sources of funding through section 6 of the Act.

(34)
Comment:
The Arizona Game and Fish Department stated that they agreed that western yellow-billed cuckoos have declined in Arizona over the last 100 years due to habitat loss. The Arizona Game and Fish Department went on to state that the western yellow-billed cuckoo population and habitat loss have stabilized over the past 30 years and populations will increase as a result of riparian restoration on the Lower Colorado River. The Arizona Game and Fish Department stated that 4,000 acres (ac) (1,619 hectares (ha)) of habitat is scheduled for restoration, and in locations where restoration has occurred, western yellow-billed cuckoos are using the created habitat within 2 years of planting. They asked us to add references that show that western yellow-billed cuckoos have declined as a result of riparian habitat loss and degradation (they cite Noss
et al.
1995). They also stated that there was a need to quantify the benefits of riparian habitat restoration to western yellow-billed cuckoos.

Our Response:
Most locations in Arizona that have western yellow-billed cuckoo populations have not been surveyed regularly enough to provide population trend information. The only two locations with semi-regular monitoring (the Bill Williams River and the San Pedro River) both show downward trends in western yellow-billed cuckoo populations. The western yellow-billed cuckoo population on the Colorado River on the Arizona-California border appears to be increasing with the riparian restoration activities at that location. More years of survey data are needed to determine whether or not that is a long-term trend.

While the results of the riparian restoration work on the Lower Colorado River are promising, based on the scientific information available we conclude that it is too soon to tell what effect this planned restoration will have on western yellow-billed cuckoo populations. As population goals for recovery of the western yellow-billed cuckoo have not yet been established, it is not known what the overall effect of an addition of the 40 or so pairs of western yellow-billed cuckoos on the Lower Colorado River will have on the overall status of the yellow-billed cuckoo in the West. In addition, so far it appears that western yellow-billed cuckoos nesting on restoration sites tend to have lower nesting success than western yellow-billed cuckoos nesting in areas still containing healthy native riparian forests (McNeil
et al.
2012, p. 53).

We have added citations in this final rule that show that western yellow-billed cuckoos have declined as a result of riparian habitat loss and degradation (see section in Factor A discussion). We have concluded that this is a well-documented pattern in California and Arizona.

To date it is difficult to quantify the benefit of riparian habitat restoration to western yellow-billed cuckoo populations. Most restoration efforts are carried out on a small scale in

comparison to the home-range size of the western yellow-billed cuckoo. In the Kern River Valley where riparian restoration has been ongoing for the past 30 years, the western yellow-billed cuckoo population has stabilized but has not increased. Along the Sacramento River, where several thousands of acres of riparian restoration has occurred over the past 30 years, the western yellow-billed cuckoo population has continued to decline. The one location where restoration work is appearing to have a positive effect on western yellow-billed cuckoo populations is along the Lower Colorado River, but this work is very recent and the long-term effect on western yellow-billed cuckoo populations there is still unknown. The largest positive effects for western yellow-billed cuckoos have occurred in the reservoir draw-down zones (e.g., Isabella Reservoir and Elephant Butte Reservoir), when riparian habitat has regenerated during droughts. These benefits are ephemeral, as the habitat will be inundated and lost when wet periods return.

New Mexico

(35)
Comment:
New Mexico Game and Fish requested a delay in listing so that more research can be conducted in New Mexico to better define the DPS line. They state that data from e-bird [Cornell Lab of Ornithology] and New Mexico Ornithological Society (2007) do not support difference in migration timing between eastern and western New Mexico, and cite Sechrist and Best (2012) to say that cuckoos from Pecos and Rio Grande had the same migration timing and direction. Twenty additional commenters questioned the DPS' status, indicating that the DPS was neither discrete nor significant, without providing additional information to support their comments.

Our Response:
In making listing determinations under the Act, we are to rely solely on the best scientific and commercial data currently available. Our DPS policy outlines the criteria for determination of whether a segment of a vertebrate species population qualifies as a DPS. In reviewing the most current information available, we have determined that the western DPS of the yellow-billed cuckoo is valid and meets the criteria outlined in our policy. As we stated above in the
Distinct Vertebrate Population Segment Analysis
section, we understand that the area in southern New Mexico and western Texas is an area where there may be overlap between both eastern and western populations of the yellow-billed cuckoo. Our DPS policy allows for some “mixing” of populations, and absolute separation is not required for a population segment of a species to be considered a DPS (61 FR 4723-4725; February 7, 1996). The location and boundaries of a western DPS for the yellow-billed cuckoo has been under consideration since the Service first received a petition to list the species in 1986. As detailed in the proposed rule and this final rule, yellow-billed cuckoos on the Rio Grande above Big Bend are more similar to yellow-billed cuckoos in the West than they are to yellow-billed cuckoos in the East. Yellow-billed cuckoos on the Pecos River and in eastern New Mexico are more similar to yellow-billed cuckoos in the East than they are to yellow-billed cuckoos in the West. Peer reviewer Dr. Janice Hughes, the only avian taxonomist who has conducted research on yellow-billed cuckoos in this region, believes that the highlands between the Rio Grande and the Pecos River are the dividing line between eastern and western yellow-billed cuckoos.

As discussed above in
Comment
14, one peer reviewer measured yellow-billed cuckoos on the Rio Grande and Pecos River and found the Rio Grande yellow-billed cuckoos to be larger than those on the Pecos River. The differences were not statistically significant, but the sample sizes were small, so a significant difference would not be expected. Also the measurements were not taken in a similar way as measurements taken by Banks (1988, pp. 473-477) and Franzreb and Laymon (1993, pp. 17-28) so they cannot be compared to measurements from those studies. At this time, a definitive study has not been completed on morphology, genetics, or behavior (including migration timing) comparing yellow-billed cuckoos on the Rio Grande and Pecos River. Until that is done, the best available science on the subject is in Franzreb and Laymon (1993, pp. 17-28) and in the opinion of Dr. Janice Hughes, which divides eastern and western yellow-billed cuckoos along the highlands separating the Rio Grande and the Pecos Rivers.

(36)
Comment:
New Mexico Game and Fish and several other commenters suggest that western yellow-billed cuckoos have been found at elevations higher than reported in the proposed rule.

Our Response:
We appreciate this additional information and have considered this in our listing determination. Most of these higher elevation sightings in the Rocky Mountains are likely of migrant western yellow-billed cuckoos, though a few may refer to nesting pairs.

(37)
Comment:
New Mexico Game and Fish would like us to develop a rule under section 4(d) of the Act to allow for economic and agricultural growth in conjunction with conservation efforts, especially while developing the State's comprehensive conservation program.

Our Response:
Section 4(d) of the Act allows the Secretary the discretion to issue such regulations as [s]he deems necessary and advisable to provide for the conservation of a species. The Service's standard policy (under 50 CFR 17.31(a)) for issuing prohibitions for threatened species is to apply all the prohibitions of an endangered species to a threatened species unless otherwise revoked by issuance of more specific prohibitions. In the case of the western yellow-billed cuckoo, we are in the process of reviewing whether the “standard” prohibitions apply or whether more specific prohibitions are appropriate. If we determine that more specific prohibitions apply and that they are necessary and advisable to provide for the conservation of the western yellow-billed cuckoo, we will issue a proposed rule under section 4(d) of the Act for public comment. However at this time, we do not have and the commenter did not provide enough information on whether a section 4(d) rule for agricultural activities is appropriate. We would be available for future discussion on potentially developing measures to maximize the conservation value of agricultural practices and develop some type of conservation mechanism with the commenter in the future; however, due to time constraints for developing a final rule we cannot currently develop and implement such measures.

(38)
Comment:
New Mexico Game and Fish stated that there was a large discrepancy between population estimates of 100-155 pairs for western New Mexico listed in the proposed rule and 7,000 individuals in the State as reported by the Partners in Flight program (PIF 2014).

Our Response:
The Partners in Flight Web site for New Mexico (New Mexico Partners in Flight 2014, entire) reports that the western yellow-billed cuckoo population in New Mexico is much less than 1 percent of the total species population of 9.2 million, or less than 92,000 yellow-billed cuckoos. This was then converted to 0.1 percent of the global population, which should have been 9,200 yellow-billed cuckoos, but was transcribed or rounded to 7,000 yellow-billed cuckoos or 3,500 pairs of yellow-billed cuckoos. This is a questionable method to determine the yellow-billed cuckoo population for a State and should not be accepted as

valid. This is much higher than Howe's (1986, pp. 1-16) estimate of 1,000 pairs of yellow-billed cuckoos Statewide in New Mexico and 315 pairs for the western half of the State. Howe's estimates were made based on an estimate of available habitat and an understanding that western yellow-billed cuckoo territories were much smaller than they actually are, leading to an overestimate for New Mexico. It is likely that fewer than 1,000 pairs of western yellow-billed cuckoos existed in New Mexico in 1986. The population for western yellow-billed cuckoos estimated for the State by Hughes (1999, p. 19) was 100 to 200 pairs. The Service's estimate of 100 to 155 pairs is based on the best available science of surveys conducted over the past 10-15 years.

(39)
Comment:
The New Mexico Department of Agriculture asked that the Service address management of the western yellow-billed cuckoo as a watershed health issue and not list the species.

Our Response:
Listing of the western yellow-billed cuckoo under the Act is based on the species' population status and trends, and the threats to the species. Recovery of a species will be based on criteria developed by the Recovery Team once it becomes established. Solving the threats to the western yellow-billed cuckoo is an important part of the recovery process, and watershed health will be very important when developing recovery criteria and implementing recovery actions.

(40)
Comment:
New Mexico Interstate Stream Commission commented that because western yellow-billed cuckoos are listed by New Mexico Fish and Game as a “Species of Greatest Conservation Need” the Service should not state that it has no protective status in New Mexico.

Our Response:
Although the identification of the western yellow-billed cuckoo by the State of New Mexico as a “Species of Greatest Conservation Need” is encouraging, this designation is for planning purposes and provides no regulatory protective status for the species in New Mexico. Any actions or conservation measures implemented for the cuckoo as a result of its State status would be recommendations and voluntary, and would not ensure that actions or measures would be implemented.

(41)
Comment:
New Mexico Interstate Stream Commission states that if the western yellow-billed cuckoo is listed, we should develop a rule under section 4(d) of the Act for ongoing and future water management in the State. Other commenters expressed concern about the impact of listing the western yellow-billed cuckoo on water delivery.

Our Response:
The disruption and changes to “natural” river and stream processes, which help the development and regeneration of riparian vegetation, have been identified as a threat to the species. The majority of streams and water delivery facilities within the range of the western yellow-billed cuckoo are at least partly managed by Federal entities or proposed activities that would have a Federal nexus. As a result, these Federal agencies have an obligation under section 7 the Act to conserve endangered or threatened species and their habitat. Section 4(d) of the Act states that the Secretary shall issue such regulations as [s]he deems necessary and advisable to provide for the conservation of any threatened species. New projects on Federal land or funding by the Federal government will be subject to section 7 consultations, as will reauthorization of Federal projects. Because of the interrelatedness between water management, the health of riparian habitat, and the dependence of riparian habitat by the western yellow-billed cuckoo, we are not currently considering a rule under section 4(d) of the Act for this species to limit the prohibitions of the Act for ongoing and future water management activities.

(42)
Comment:
The New Mexico Interstate Stream Commission stated that because humans do not have control over caterpillar population, lack of caterpillars should not be listed as a threat.

Our Response:
Caterpillar and other insect populations can be affected by health of the riparian habitat, tree and shrub species in the riparian zone, and pesticide use (e.g., pesticide drift into the riparian zone or applying pesticides directly on the riparian zone). All of these factors are influenced by human activities at some level. Lack of an adequate food supply is a major threat for the western yellow-billed cuckoo.

(43)
Comment:
The New Mexico Interstate Stream Commission stated that climate change effects have so far not been as great as they are predicted to be in the future.

Our Response:
We appreciate the New Mexico Interstate Stream Commission's comments on climate change and have considered them in our listing determination. The New Mexico Department of Game and Fish in their Comprehensive Wildlife Conservation Strategy for New Mexico (2006) stated that “[t]he effects of climate change on ecosystems and species are likely to be exacerbated in areas that have already been substantially affected by human activities such as habitat loss and fragmentation, air and water pollution, and the establishment of invasive species.” They also state that riparian habitat is one of the key habitats that may have the highest risk of being altered by synergistic effects of factors that influence habitats (New Mexico Department of Game and Fish. 2006, pp. 74-79).

We agree that climate change projections and prediction can be difficult due to the availability of information and variability of climate and habitat conditions over time. However, in a study looking at the recent effects of climate change on temperature and precipitation over the past 36+ years (1970-2006), Enquist
et al.
(2008, pp. 1-32) found that in New Mexico, observed climate-linked effects include declines in snowpack, earlier peak stream flows, forest mortality, and population declines in some sensitive species. To avoid issues of uncertainty associated with future climate change predictions, the study used a retrospective approach that analyzed changes over time. Their study found that: (1) 93 Percent of New Mexico's watersheds have become relatively drier over the 36+ year period; and (2) snowpack has declined in 98 percent of New Mexico's major mountain ranges and the timing of peak streamflow from snowmelt in the State is an average of one week earlier than in the 1950s. In addition, the study found that the watersheds with the highest numbers of sensitive species tend be those showing the greatest increase in moisture stress or drying and that these watersheds have already experienced climate change-linked ecological effects. We have determined that the long-term effects of climate change are and will continue to be a factor in sensitive species or habitat conservation regardless of any short-term trends.

(44)
Comment:
The New Mexico Interstate Stream Commission commented that western yellow-billed cuckoos may rely on tamarisk, like southwestern willow flycatchers do, but even if true, tamarisk beetles should not be listed as a threat to western yellow-billed cuckoos.

Our Response:
Western yellow-billed cuckoos do not rely on tamarisk in the same way that southwestern willow flycatchers do. Western yellow-billed cuckoos may on rare occasions nest in tamarisk, but they forage almost entirely in native riparian habitat. Western yellow-billed cuckoos are primarily dependent on large caterpillars, which depend on cottonwoods and willows and are not found on tamarisk. On the other hand, southwestern willow

flycatchers feed on small flying insects and both nest and forage in tamarisk as long as water or super-saturated soil is in the vicinity of the nest and flying insects are available. In areas where the hydrology is still intact and will support native riparian habitat, the tamarisk beetle could assist in the restoration of the riparian zone. In areas that can no longer support willows, cottonwoods, and mesquite, the beetle could suppress the tamarisk to the point that western yellow-billed cuckoos will no longer use the habitat. In this latter case, the tamarisk beetle could be considered a threat, as spontaneous regeneration of native vegetation is difficult due to the degraded nature of the habitat and disrupted hydrologic conditions.

Texas

(45)
Comment:
The Deputy Commissioner for the Texas General Land Office stated that listing the western yellow-billed cuckoo would lead to increased economic costs and delay in the development of oil, gas, wind, and solar projects for the State. Royalties collected by the State from such activities would be reduced, and this would indirectly affect funds available for Texas public schools. The Deputy Commissioner also stated that the Service's analysis of the information is not sufficient to support listing and that the Service is only moving forward at this time with listing due to its settlement with outside litigants and not because listing is warranted under the Act.

Our Response:
Under section 4(a)(1) of the Act, we are to determine if a species is endangered or threatened based on one of five listing factors. Economics or loss of revenue is not one of the factors used in determining if a species should be listed. Although we understand that listing a species as either endangered or threatened causes some regulatory oversight and the potential need for consultation, we are obligated to make such determinations solely on the threats facing the species or its habitat. Listing a species does not mean projects cannot proceed, it only means they must be implemented in a manner that still conserves the species and its habitat. In addition, because the species occurs in riparian habitat along streams, it is most likely that projects involving the development of oil, gas, wind, and solar projects would not result in significant direct impacts on the species, as these projects typically do not occur in riparian corridors.

We believe we have used the best scientific and commercial information available in coming to our decision to list the western yellow-billed cuckoo as a threatened species. The western yellow-billed cuckoo has been a candidate for listing since 2001. Although we were litigated to develop a timeframe for moving forward on the review of candidate species, the Act requires us to promptly make our evaluations for species considered candidates. Any settlements reached as a result of litigation took into consideration what was best for conservation and protection of candidate or sensitive species and were not dictated by litigants.

(46)
Comment:
The Texas Comptroller of Public Accounts stated that they were concerned that listing of the western yellow-billed cuckoo would have potential economic impacts on landowners, businesses, and communities within the boundary of the DPS in Texas. The Comptroller also stated that additional information is needed on the status of the species and that the benefits of ongoing conservation efforts for the southwestern willow flycatcher are adequate to conserve the western yellow-billed cuckoo.

Our Response:
See our response to
Comment
45 above for economic considerations in the listing process and our view on the information used to determine the status of the species. In regard to conservation measures for the southwestern willow flycatcher being adequate to conserve the western yellow-billed cuckoo, we disagree. Although the range of the southwestern willow flycatcher and the western yellow-billed cuckoo overlap to some degree and they are found in similar habitats, that is not always the case and the two species have very different habitat and ecological requirements.

Public Comments

Comments on “Endangered” vs. “Threatened” Status

(47)
Comment:
More than 12,000 commenters stated that the western yellow-billed cuckoo should be listed as “endangered” rather than the proposed “threatened” status.

Our Response:
The Act defines an endangered species as any species that is currently “in danger of extinction throughout all or a significant portion of its range” and a threatened species as any species “that is likely to become endangered throughout all or a significant portion of its range within the foreseeable future.” Based on the available information on the range and distribution of the species, the immediacy and severity of threats facing the species, the persistence of the species throughout most of its historical range, and the rate of decline of the species, we have determined that the western yellow-billed cuckoo meets the definition of a threatened species rather than an endangered species under the Act. See the
Determination
section below for additional discussion of our rationale for a “threatened” determination.

(48)
Comment:
One commenter stated that the entire species (both in the eastern and western United States) should be listed as a threatened species under the Act.

Our Response:
Our analysis in the rule is limited to the petitioned entity (western United States), and we have not evaluated the status of the eastern population of the yellow-billed cuckoo. Should new information become available about the status, trends, or threats facing the eastern population of the yellow-billed cuckoo, we would evaluate that information at that time, as budget and staffing allow.

Comments on the Distinct Population Segment

(49)
Comment:
One commenter stated that the western DPS of the yellow-billed cuckoo also meets significance because of persistence of population on unusual or unique ecological setting (i.e., streamside riparian areas in arid West).

Our Response:
We appreciate this additional information and have considered this in our listing determination. Yellow-billed cuckoos in both the East and West nest in riparian habitat. The species in the eastern United States has a wider range of habitat use, including nesting in upland broadleaf woodlands that are not available to the species in the West. We do not consider riparian habitat as unusual or unique habitat under our DPS policy.

(50)
Comment:
Several commenters stated that there had been too many studies on the yellow-billed cuckoo and other commenters stated that there had been too few studies. Genetics and taxonomic uniqueness was a suggested area of study by one commenter.

Our Response:
Although there has been much focus on research on the yellow-billed cuckoo, most of these efforts have been on survey and monitoring. Additional research activity is a common response once a species is identified for listing under the Act. However, other information, such as migratory routes, timing, and wintering ground use, has been scarce, and we agree that there are many areas of the life history, ecology, genetics, and taxonomy of the western yellow-billed cuckoo that need further research. However, in making our listing

determination, we must use the best scientific and commercial data available in coming to any conclusions on whether the species should be listed.

(51)
Comment:
One commenter stated that the eastern and western yellow-billed cuckoos may be interbreeding on the wintering grounds.

Our Response:
Because yellow-billed cuckoos do not breed on their wintering grounds in South America, it is not plausible that they are interbreeding during this time.

(52)
Comment:
Several commenters do not believe that differences in migration timing between eastern and western yellow-billed cuckoos are evidence that there is a marked separation between the two groups.

Our Response:
The proposed rule and this final rule identify a wide variety of factors that separates western yellow-billed cuckoos from the rest of the taxon. Migration timing is one of these factors. In general, migration timing is governed by forces of natural selection that operate over long periods of time. Given that populations of eastern and western yellow-billed cuckoos arrive on their breeding grounds, at the same latitude, a month or more apart is significant and is most likely governed by evolutionary forces. This pattern of consistently arriving on their respective breeding grounds a month or more apart is different from year to year, and variations in weather may lead to individual birds arriving on the breeding grounds a few days earlier or later than normal. Please see the
Distinct Vertebrate Population Segment Analysis
section, above, for further explanation of our rationale for determining that the western yellow-billed cuckoo is a valid DPS.

(53)
Comment:
Three commenters stated that they believed that the species was not distinct.

Our Response:
The Service is listing a DPS rather than a species or subspecies. As detailed in the
Taxonomy
section under
Background
and
Discreteness
section of the
Distinct Vertebrate Population Segment Analysis
above, the western DPS of the yellow-billed cuckoo coincides with the range of the proposed subspecies boundary of the “western” yellow-billed cuckoo (
Coccyzus americanus occidentalis
). However, because there is some scientific uncertainty to the validity of the subspecies, the Service is not listing the subspecies, but rather is listing the western DPS.

Population Numbers

(54)
Comment:
Twelve commenters stated that there have been recent declines of breeding populations of western yellow-billed cuckoos in various locations of California, Arizona, New Mexico, and Colorado. Several additional commenters provided their personal observations in Arizona, New Mexico, and Colorado, which indicated that local populations of western yellow-billed cuckoos have declined over the last 30 years.

Our Response:
These additional observations support the information that we presented in the proposed and this final listing rule regarding population trends for the species in these States.

(55)
Comment:
Nine commenters stated that the western yellow-billed cuckoo was not threatened, that they were either not declining or not declining at a rate that would lead to extinction, and that yellow-billed cuckoos were doing well in the East.

Our Response:
Yellow-billed cuckoos in the East are declining at 1.4 to 1.6 percent per year over the past 43 years (Sauer
et al.
2012, entire). Based on the best available science and data, western yellow-billed cuckoos have declined dramatically throughout their range over the past 150 years. This decline has continued in recent years, and with very few exceptions (e.g., the South Fork Kern River Valley, where the small populations appears to be stable, and the Lower Colorado River, where the population is showing an increase), it is continuing to decline. The data and information we have used in this final rule lead us to conclude that the western DPS of the yellow-billed cuckoo is threatened with extinction. No data were presented by commenters that show increasing population trends or population numbers that contradict our conclusion that the western yellow-billed cuckoo is a threatened species.

(56)
Comment:
Eight comments were received on data analysis and proposed rule preparation. Issues raised included the lack of a population viability analysis, the lack of a global population analysis, inadequate citations support for statements made in the document, not providing the names of Service biologists who reviewed data, taking a California-centric approach in the proposed rule, and only providing range maps showing the breeding season's range.

Our Response:
Current available scientific data on the western yellow-billed cuckoo are not sufficient to conduct a meaningful population viability analysis. Too many of the important parameters are not known well enough for the results to be reliable. The State-by-State and region-by-region analysis of the entire range of the western DPS of the yellow-billed cuckoo is essentially a global population analysis. Every attempt has been made to be certain that citations support the statements made in the proposed and this final rule. Where we do not have specific reference support we explained our rationale based on the best available information on coming to any conclusions. It is not Service policy to list names of document authors or those who reviewed data. Much of the research that has been conducted on the western yellow-billed cuckoos has occurred in California, which may lead readers to the opinion that the proposed rule is California-centric. The winter range of the western yellow-billed cuckoo is not well-known and therefore could not be mapped.

(57)
Comment:
Several commenters stated that western yellow-billed cuckoo survey data were missing from the proposed rule or the data have been updated after the proposed rule was published (e.g., Utah, New Mexico, Arizona).

Our Response:
We have considered this updated information in our final listing determination, and the information will be considered in the final critical habitat designation and future recovery plan.

(58)
Comment:
One commenter asked why western yellow-billed cuckoos are continuing to decline with all the habitat protection that has been happening over the past 25 years.

Our Response:
It is true that significant habitat protection and restoration has been underway for the past 25 to 30 years. Much of this work has been done on a project-by-project basis or on a smaller scale than will likely be necessary for the stabilization and recovery of the species. Recovery goals for western yellow-billed cuckoos and their habitat will be set in the recovery plan for the species as it is developed. In some areas, such as the Sacramento River, western yellow-billed cuckoo populations have continued to decline even though significant habitat restoration activities have been carried out. Aging of the existing habitat and increased occupancy by invasive species, especially edible fig (
Ficus carica
) and black walnut (
Juglans
sp.), may be contributing factors. In addition, effects of pesticides on caterpillars may be a factor in many areas. It is indeed a concern that western yellow-billed cuckoos have declined even in areas where habitat has been protected and has either been stabilized or has increased. Further research is needed to determine the exact causes of this continued decline.

(59)
Comment:
One commenter questioned our science and asked that

all information on western yellow-billed cuckoo populations and declines should be removed from the discussion in the rule.

Our Response:
The information on western yellow-billed cuckoo population and declines presented in the proposed and this final rule is based on the best available science. In making listing determinations under the Act, we must conduct a five-factor analysis on the threats facing a species based on the best available scientific and commercial information. In some cases the information on a species' status and trends is unclear or the information available is sparse. In these cases, we nonetheless must base our determinations on the best available information. In the case of the western yellow-billed cuckoo, the available information on population status and declines is appropriate to include in our discussion of the status of the species and in making our final determination on the species' listing status of threatened.

(60)
Comment:
Numerous commenters have concerns regarding survey methods, compar

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2014-23640. Public record. Not legal advice.