Federal Register / Vol. 75, No. 37 / Thursday, February 25, 2010 / Proposed Rules 8601 

ii. EPA recommends, but does not require, that water solubility be quantitatively estimated prior to initiating this study. One method, among 

many similar methods, for estimating water solubility is described in the article entitled ‘‘Improved Method for Estimating Water Solubility From 

Octanol/Water Partition Coefficient’’ by W.M. Meylan, P.H. Howard, and R.S. Boethling in Environmental Toxicology and Chemistry. 15(2):100– 

106. 1996. This reference is available under docket ID number EPA–HQ–OPPT–2007–0531 at the EPA Docket Center, Rm. 3334 in the EPA 

West Bldg. located at 1301 Constitution Ave., NW., Washington, DC, from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. 

iii. Chemical substances that are dispersible in water may have log Kow values greater than 4.2 and may still be acutely toxic to aquatic organisms. Test sponsors who wish to conduct Test Group 1 studies on such chemical substances may request a modification to the test standard 

as described in 40 CFR 790.55. Based upon the supporting rationale provided by the test sponsor, EPA may allow an alternative threshold or 

method be used for determining whether acute or chronic aquatic toxicity testing be performed for a specific substance. 

iv. The OECD 425 Up/Down Procedure, revised by OECD test guidelines in December 2001, is available under docket ID number EPA–HQ– 

OPPT–2007–0531 at the EPA Docket Center, Rm. 3334 in the EPA West Bldg. located at 1301 Constitution Ave., NW., Washington, DC, from 

8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. 

v. The neutral red uptake basal cytotoxicity assay, which may be used to estimate the starting dose for the mammalian toxicity-acute endpoint, 

is available under docket ID number EPA–HQ–OPPT–2007–0531 at the EPA Docket Center, Rm. 3334 in the EPA West Bldg. located at 1301 

Constitution Ave., NW., Washington, DC, from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. 

(k) Effective date. This section is 

effective on [30 days after date of 

publication of the final rule in the 

Federal Register]. 

[FR Doc. 2010–3734 Filed 2–24–10; 8:45 am] 

BILLING CODE 6560–50–S 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–R2–ES–2008–0059; MO 

92210–0–0008] 

Endangered and Threatened Wildlife 

and Plants; 12-Month Finding on a 

Petition To List the Sonoran Desert 

Population of the Bald Eagle as a 

Threatened or Endangered Distinct 

Population Segment 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: 12-month petition finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce a 

12-month finding on a petition to list 

the Sonoran Desert Area population of 

the bald eagle (Haliaeetus 

leucocephalus) as a distinct population 

segment (DPS). In the petition, we were 

asked that the DPS be recognized, listed 

as endangered, and that critical habitat 

be designated under the Endangered 

Species Act of 1973, as amended (Act). 

After review of all available scientific 

and commercial information, we find 

that the Sonoran Desert Area population 

of the bald eagle does not meet the 

definition of a DPS and, therefore, is not 

a listable entity under the Act. As a 

result, listing is not warranted, and we 

intend to publish a separate notice to 

remove this population from the List of 

Threatened and Endangered Wildlife 

once the District Court for the District of 

Arizona has been notified. We ask the 

public to continue to submit to us any 

new information that becomes available 

concerning the taxonomy, biology, 

ecology, and status of this population of 

the bald eagle and to support 

cooperative conservation of the bald 

eagle within the Sonoran Desert Area. 

DATES: The finding announced in this 

document was made on February 25, 

2010. 

ADDRESSES: This finding is available on 

the Internet at http:// 

www.regulations.gov at Docket Number 

[FWS–R2–ES–2008–0044]. Supporting 

documentation for this finding is 

available for inspection, by 

appointment, during normal business 

hours at the Arizona Ecological Services 

Office, 2321 West Royal Palm Road, 

Suite 103, Phoenix, AZ 85021–4951. 

Please submit any new information, 

materials, comments, or questions 

concerning this species or this finding 

to the above address, Attention: Sonoran 

Desert Area bald eagle. 

FOR FURTHER INFORMATION CONTACT: 

Steve Spangle, Field Supervisor, 

Arizona Ecological Services Office (see 

ADDRESSES); telephone, 602–242–0210; 

facsimile, 602–242–2513. If you use a 

telecommunications device for the deaf 

(TDD), call the Federal Information 

Relay Service (FIRS) at 800–877–8339. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(B) of the Act (16 

U.S.C. 1531 et seq.) requires that, for 

any petition to revise the Lists of 

Endangered and Threatened Wildlife 

and Plants that contains substantial 

scientific or commercial information 

that listing may be warranted, we make 

a finding within 12 months of the date 

of our receipt of the petition on whether 

the petitioned action is: (a) Not 

warranted, (b) warranted, or (c) 

warranted, but the immediate proposal 

of regulation implementing the 

petitioned action is precluded by other 

pending proposals to determine whether 

species are threatened or endangered, 

and expeditious progress is being made 

to add or remove qualified species from 

the List of Endangered and Threatened 

Wildlife and Plants. Section 4(b)(3)(C) of 

the Act requires that we treat a petition 

for which the requested action is found 

to be warranted but precluded as though 

resubmitted on the date of such finding, 

that is, requiring that we make a 

subsequent finding within 12 months. 

Such 12-month findings must be 

published in the Federal Register. 

This notice constitutes our 12-month 

finding on a petition to list the Sonoran 

Desert Area bald eagle. In this 

document, the Sonoran Desert Area 

population is the name given to the 

entity under evaluation for designation 

as a DPS. For the purposes of this 

assessment, the Sonoran Desert Area 

population includes all bald eagle 

territories within Arizona, the Copper 

Basin breeding area in California near 

the Colorado River, and the territories of 

interior Sonora, Mexico, that occur 

within the Sonoran Desert or adjacent, 

transitional communities. For more 

detail on the boundary of the DPS, see 

the discussion below under 

Determination of the Area for Analysis. 

Previous Federal Action 

Bald eagles gained protection under 

the Bald Eagle Protection Act (16 U.S.C. 

668–668d) in 1940 and the Migratory 

Bird Treaty Act (MBTA) (16 U.S.C. 703– 

712) in 1972. A 1962 amendment to the 

Bald Eagle Protection Act added 

protection for the golden eagle and the 

amended statute became known as the 

Bald and Golden Eagle Protection Act 

(BGEPA). On March 11, 1967 (32 FR 

4001), the Secretary of the Interior listed 

bald eagles south of 40 north latitude as 

endangered under the Endangered 

Species Preservation Act of 1966 (Pub. 

L. 89–699, 80 Stat. 926) due to a 

population decline caused by dichlorodiphenyltrichloroethane (DDT) and 

other factors. On February 14, 1978, the 

Service listed the bald eagle as an 

endangered species under the Act (16 

U.S.C. 1531 et seq.) in 43 of the 

contiguous States, and as a threatened 

species in the States of Michigan, 

Minnesota, Wisconsin, Oregon, and 

Washington (43 FR 6230). Sub-specific 

designations for northern and southern 

eagles were removed. 


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On February 7, 1990, we published an 

advance notice of proposed rulemaking 

(55 FR 4209) to reclassify the bald eagle 

from endangered to threatened in the 43 

States where it had been listed as 

endangered and retain the threatened 

status for the other five States. On July 

12, 1994, we published a proposed rule 

to accomplish this reclassification (59 

FR 35584), and the final rule was 

published on July 12, 1995 (60 FR 

36000). 

On July 6, 1999, we published a 

proposed rule to delist the bald eagle 

throughout the lower 48 States due to 

recovery (64 FR 36454). On February 16, 

2006, we reopened the public comment 

period to consider new information 

received on our July 6, 1999 (71 FR 

8238), proposed rule to delist the bald 

eagle in the lower 48 States. The 

reopening notice contained updated 

information on several State survey 

efforts and population numbers. 

Simultaneously with the reopening of 

the public comment period on the 

proposed delisting, we also published 

two Federal Register documents 

soliciting public comments on two new 

items intended to clarify the BGEPA 

protections for the bald eagle after 

delisting: (1) A proposed rule for a 

regulatory definition of ‘‘disturb’’ (71 FR 

8265), and (2) a notice of availability for 

draft National Bald Eagle Management 

Guidelines (71 FR 8309). On May 16, 

2006, we published three separate 

notices in the Federal Register that 

extended the public comment period on 

the proposed delisting (71 FR 28293), 

the proposed regulatory definition of 

‘‘disturb’’ (71 FR 28294), and the draft 

guidelines (71 FR 28369). The comment 

period for all three documents was 

extended to June 19, 2006. 

Between publication of the July 6, 

1999, proposed rule to delist the bald 

eagle and the February 16, 2006, 

reopening of the comment period on the 

proposed rule to delist the bald eagle, 

we received a petition regarding bald 

eagles in the southwestern United 

States. On October 6, 2004, we received 

a petition from the Center for Biological 

Diversity (CBD), the Maricopa Audubon 

Society, and the Arizona Audubon 

Council requesting that the 

‘‘Southwestern desert nesting bald eagle 

population’’ be classified as a DPS, that 

this DPS be reclassified from a 

threatened species to an endangered 

species, and that we concurrently 

designate critical habitat for the DPS 

under the Act. 

On March 27, 2006, the CBD and the 

Maricopa Audubon Society filed a 

lawsuit against the U.S. Department of 

the Interior and the Service for failing to 

make a timely finding on the petition. 

The parties reached a settlement, and 

the Service agreed to complete its 

petition finding by August 2006. We 

announced in our 90-day finding on 

August 30, 2006 (71 FR 51549), that the 

petition did not present substantial 

scientific or commercial information 

indicating that the petitioned action 

may be warranted. 

On January 5, 2007, the CBD and the 

Maricopa Audubon Society filed a 

lawsuit challenging the Service’s 90-day 

finding that the ‘‘Sonoran Desert 

population’’ of the bald eagle did not 

qualify as a DPS, and further 

challenging the Service’s 90-day finding 

that the population should not be 

uplisted to endangered status. 

On July 9, 2007 (72 FR 37346), we 

published the final delisting rule for 

bald eagles in the lower 48 States. This 

final delisting rule also constituted the 

Service’s final determination on the 

status of the Sonoran Desert population 

of bald eagles. In that final delisting 

rule, we stated that our findings on the 

status of the Sonoran Desert population 

of bald eagles superseded our 90-day 

petition finding because the final 

delisting rule constituted a final 

decision on the DPS determination. This 

determination was based on a thorough 

review of the best available data, which 

indicated that the threats to the species 

had been eliminated or reduced to the 

point that the species had recovered and 

no longer met the definition of a 

threatened or endangered species under 

the Act. It addressed the same issues 

that the Service would have considered 

as part of a 12-month finding had the 

Service made a positive 90-day finding 

on the petition and then subsequently 

conducted the required status review. 

We determined that the final delisting 

rule therefore rendered moot any issues 

regarding the 90-day petition finding. 

On August 17, 2007, the CBD and the 

Maricopa Audubon Society filed a 

Motion for Summary Judgment, 

requesting the court to make a decision 

on their January 5, 2007, lawsuit. In 

early 2008, several Native American 

Tribes submitted amicus curiae (‘‘friend 

of the court’’) briefs in support of the 

August 17, 2007, Motion for Summary 

Judgment. The San Carlos Apache Tribe, 

Yavapai-Apache Nation, and Tonto 

Apache Tribe submitted an amicus 

curiae brief to the court on January 29, 

2008; the Salt River Pima-Maricopa 

Indian Community submitted an amicus 

curiae brief to the court on February 4, 

2008; and the Fort McDowell Yavapai 

Nation submitted an amicus curiae brief 

to the court on February 7, 2008. 

On March 5, 2008, the U.S. District 

Court for the District of Arizona made 

a final decision in the case and ruled in 

favor of the CBD and the Maricopa 

Audubon Society. The court order 

(Center for Biological Diversity v. 

Kempthorne, CV 07–0038–PHX–MHM 

(D. Ariz)), was filed on March 6, 2008. 

The court: 

(1) Ordered the Service to conduct a 

status review of the Desert bald eagle 

population pursuant to the Act to 

determine whether listing that 

population as a DPS is warranted, and 

if so, whether listing that DPS as 

threatened or endangered pursuant to 

the Act is warranted; 

(2) Ordered the Service to issue a 12- 

month finding on whether listing the 

Desert bald eagle population as a DPS is 

warranted, and if so, whether listing 

that DPS as threatened or endangered is 

warranted; 

(3) Ordered the Service to issue the 

12-month finding within 9 months of 

the court order pursuant to 16 U.S.C. 

1533(b)(3)(B), which translates to on or 

before December 5, 2008; 

(4) Enjoined the Service’s application 

of the July 9, 2007 (72 FR 37346), final 

delisting rule to the Sonoran Desert 

population of bald eagles pending the 

outcome of our status review and 12- 

month petition finding. 

On May 1, 2008, we published a final 

rule designating bald eagles within the 

Southwest as a DPS for purposes of 

conforming to the court-ordered 

requirement to retain listing status as 

threatened for those bald eagles in the 

petitioned area (73 FR 23966). A map of 

the DPS for that action was included in 

the rule. 

On May 20, 2008, we published a 

Federal Register notice (73 FR 29096) 

initiating a status review for the bald 

eagle in the Sonoran Desert Area of 

central Arizona and Northwestern 

Mexico. The information collection 

period remained open until July 7, 2008. 

Additional comments were received and 

considered beyond this date as 

discussed below. 

On August 27, 2008, the CBD and 

Maricopa Audubon Society filed an 

unopposed motion (CV07–0038–PHX– 

MHM) to amend the March 6, 2008, 

court order by extending the completion 

date of the status review of the Desert 

bald eagle population until October 12, 

2009. Supporting declarations were 

filed by the Salt River Pima-Maricopa 

Indian Community, the Inter Tribal 

Council of Arizona, and Joe P. Sparks. 

The motion was granted on August 29, 

2008. 

On September 14, 2009, the Service 

filed an unopposed motion to amend 

the March 6, 2008, court order by 

extending the completion date of the 

status review of the Sonoran Desert bald 

eagle population until February 12, 


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2010 (CV07–0038–PHX–MHM). The 

motion was granted on September 25, 

2009, and a second extension was put 

in place. 

On February 11, 2010, the Service 

filed, and was granted, an unopposed 

motion for a one week extension, 

extending the completion date to 

February 19, 2010. 

Public Information 

As noted above, on May 20, 2008, the 

Service published a notice to initiate a 

12-month status review for the Sonoran 

Desert population of bald eagle in 

central Arizona and northwestern 

Mexico, and a solicitation for new 

information. To allow adequate time to 

consider the information, we requested 

that information be submitted on or 

before July 7, 2008. On January 15, 

2009, a second Federal Register notice 

(74 FR 2465) was published announcing 

the continuation of information 

collection for the 12-month status 

review. In order to allow us adequate 

time to consider and incorporate 

submitted information, we requested 

that we receive information on or before 

July 10, 2009. Between May 2008 and 

the time that we published this 

document, 31 responses were submitted 

to http://www.regulations.gov and 5 

letters were received by U.S. mail. 

Tribal Information 

In accordance with Secretarial Order 

3206, the Service acknowledges our 

responsibility to consult with Federally 

recognized Tribes on a government-togovernment basis. Over the course of the 

bald eagle status review, we have 

corresponded and met with various 

Tribes in Arizona, all of whom support 

protection of the bald eagle under the 

Act. On July 2, 2008, the Service and 

Tribal representatives from four Western 

Apache Tribes and one Nation (White 

Mountain Apache, San Carlos Apache, 

Tonto Apache Tribes, and YavapaiApache Nation) met to hear testimony 

from cultural authorities on a variety of 

subjects including the history of the 

eagle in Arizona, and the importance of 

the eagle to the Apache people. At the 

request of Tribal representatives, this 

meeting was recorded and incorporated 

into the administrative record for the 

12-month finding. On July 3, 2008, the 

Service met with members of the Salt 

River Pima-Maricopa Indian 

Community, Gila River Indian 

Community, Tohono O’Odham Nation, 

Ak-Chin Indian Community, Tonto 

Apache Tribe, Fort McDowell Yavapai 

Nation, the Hopi Tribe, Pascua Yaqui 

Tribe, Zuni Tribe, and the InterTribal 

Council of Arizona. This meeting was 

held in Phoenix, Arizona, and a court 

reporter was present recording the 

meeting minutes. Members of the Tribes 

and nations present, however, did not 

consider this meeting government-togovernment consultation pursuant to 

Secretarial Order 3206. On July 20, 

2009, an official consultation meeting 

between the Service and Salt River 

Pima-Maricopa Indian Community 

occurred. Written comments were 

provided by the Western Apache Tribes 

and Nation and the Salt River PimaMaricopa Indian Community on July 10, 

2009. 

Although comments from the Native 

American communities were provided 

in writing, much of the knowledge 

about the bald eagle was offered during 

the above-referenced face-to-face 

meetings. Native American knowledge 

about the eagle is passed down orally 

from one generation to the next, which 

is often referred to in the literature as 

traditional ecological knowledge. 

Traditional ecological knowledge refers 

to the knowledge base acquired by 

indigenous and local peoples over many 

hundreds of years through direct contact 

with the environment. Traditional 

knowledge is based in the ways of life, 

belief systems, perceptions, cognitive 

processes, and other means of 

organizing and transmitting information 

in a particular culture. Traditional 

ecological knowledge includes an 

intimate and detailed knowledge of 

plants, animals, and natural 

phenomena; the development and use of 

appropriate technologies for hunting, 

fishing, trapping, agriculture, and 

forestry; and a holistic knowledge, or 

‘‘world view,’’ which parallels the 

scientific discipline of ecology (Inglis 

1993, p. vi). 

Testimony by the Western Apache 

Tribes and Nation and Salt River PimaMaricopa Indian Community clearly 

demonstrates the importance of the bald 

eagle to their culture, its relevance to 

their well-being, and their respect for its 

power. Their testimony also 

demonstrates the Western Apache and 

Salt-River Pima Maricopa knowledge 

base of the bald eagle and its habitat. 

The Native American relationship with 

the bald eagle in the Sonoran Desert 

Area predates modern Western 

scientific knowledge of the bald eagle by 

thousands of years (Lupe et al. pers. 

comm. 2008, p. 1). Given the expertise 

and traditional ecological knowledge 

about the bald eagle in the Southwest by 

the Western Apache Tribes and Nation 

and Salt-River Pima Maricopa Indian 

Community, we have attempted to 

incorporate their indigenous knowledge 

and information into our status review 

and 12-month finding. 

Species Information 

The bald eagle (Haliaeetus 

leucocephalus) is the only species of sea 

eagle regularly occurring in North 

America (60 FR 35999; July 12, 1995). 

Literally translated, H. leucocephalus 

means white-headed sea eagle. Bald 

eagles are birds of prey of the Order 

Falconiformes and Family Accipitridae. 

They vary in length from 28 to 38 inches 

(in) (71 to 96 centimeters (cm)), weigh 

between 6.6 and 13.9 pounds (lbs) (3.0 

and 6.3 kilograms (kg)), and have a 66- 

to 96-in (168- to 244-cm) wingspan. 

Distinguishing features of adult bald 

eagles include a white head, tail, and 

upper- and lowertail-coverts; a dark 

brown body and wings; and a yellow 

iris, beak, leg, and foot. Immature bald 

eagles are mostly dark brown and lack 

a white head and tail until they reach 

approximately 5 years of age (Buehler 

2000, p. 2). 

Biology and Distribution 

Though once considered endangered, 

the bald eagle population in the lower 

48 States has increased considerably in 

recent years. Regional bald eagle 

populations in the Northwest, Great 

Lakes, Chesapeake Bay, and Florida 

have increased five-fold in the past 20 

years. Bald eagles are now repopulating 

areas throughout much of the species’ 

historical range that were unoccupied 

only a few years ago. 

The bald eagle ranges throughout 

much of North America, nesting on both 

coasts from Florida to Baja California, 

Mexico in the south, and from Labrador 

to the western Aleutian Islands, Alaska, 

in the north. Fossil records indicate that 

bald eagles inhabited North America 

approximately 1 million years ago, but 

they may have been present before that 

(Stahlmaster 1987, p. 5). An estimated 

quarter to a half million bald eagles 

lived on the North American continent 

before the first Europeans arrived. 

In many Western Apache groups, the 

bald eagle is called Istlga ́ı ́, which 

translates to ‘‘the white eagle’’ and is 

distinguished from the golden eagle, 

which is called Itsa Cho or ‘‘the big 

eagle.’’ The bald eagle was first 

described in Western culture in 1766 as 

Falco leucocephalus by Linnaeus. This 

South Carolina specimen was later 

renamed as the southern bald eagle, 

subspecies Haliaeetus leucocephalus 

leucocephalus (Linnaeus) when 

Townsend identified the northern bald 

eagle as Haliaeetus leucocephalus 

alascanus in 1897 (Buehler 2000, p. 4). 

By the time the bald eagle was listed 

throughout the lower 48 States under 

the Endangered Species Act in 1978, 

ornithologists no longer recognized the 


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subspecies (American Ornithologists 

Union 1983, p. 106). 

The bald eagle is a bird of aquatic 

ecosystems. It frequents estuaries, large 

lakes, reservoirs, major rivers, and some 

seacoast habitats. Fish is the major 

component of its diet, but waterfowl, 

gulls, and carrion are also eaten. The 

species may also use prairies if adequate 

food is available. Bald eagles usually 

nest in trees near water, but are known 

to nest on cliffs and (rarely) on the 

ground. The trees must be sturdy and 

open to support a nest that is often 5 

feet (ft) (1.52 meters (m)) wide and 3 ft 

(0.91 m) deep. Adults tend to use the 

same breeding areas year after year, and 

often the same nest, though a breeding 

area may include one or more alternate 

nests. Nest shape and size vary, but 

typical nests are approximately 4.9 to 

5.9 ft (1.5 to 1.8 m) in diameter and 2.3 

to 4.3 ft (0.7 to 1.2 m) tall (Stahlmaster 

1987, p. 53). In winter, bald eagles often 

congregate at specific wintering sites 

that are generally close to open water 

and offer good perch trees and night 

roosts. 

Bald eagles are long-lived. One of the 

longest-living bald eagles known in the 

wild was reported near Haines, Alaska, 

as 28 years old (Schempf 1997, p. 150). 

In 2009, a female eagle nesting at Alamo 

Lake in Arizona turned 30 years old (J. 

Driscoll, Arizona Game and Fish 

Department (AGFD), pers. comm. 2009). 

In captivity, bald eagles may live 40 or 

more years. It is presumed that once 

they mate, the bond is long-term. 

Variations in pair bonding are known to 

occur. If one mate dies or disappears, 

the other will accept a new partner. 

Bald eagle pairs begin courtship about 

a month before egg-laying. In the south, 

courtship occurs as early as September, 

and in the north, as late as May. The 

nesting season lasts about 6 months. 

Incubation lasts approximately 35 days, 

and fledging takes place at 11 to 12 

weeks of age. Parental care may extend 

4 to 11 weeks after fledging (Hunt et al. 

1992, p. C9; Wood et al. 1998, pp. 336– 

338). The fledgling bald eagle is 

generally dark brown except the 

underwing linings, which are primarily 

white. Between fledging and adulthood, 

the bald eagle’s appearance changes 

with feather replacement each summer. 

Young, dark bald eagles may be 

confused with the golden eagle, Aquila 

chrysaetos. The bald eagle’s distinctive 

white head and tail are not apparent 

until the bird fully matures, usually at 

4 to 5 years of age. 

The migration strategies for breeding, 

nonbreeding, and juvenile or subadult 

age classes of bald eagles will vary 

depending on geographic location. 

Young eagles may wander widely for 

years before returning to nest in natal 

areas. Northern bald eagles winter in 

areas such as the Upper Mississippi 

River, Great Lakes shorelines, and river 

mouths in the Great Lakes area. For 

midcontinent bald eagles, wintering 

grounds may be the southern States, and 

for southern bald eagles, whose nesting 

may begin in the winter months, the 

nonbreeding season foraging areas may 

be the Chesapeake Bay or Yellowstone 

National Park during the summer. 

Eagles seek wintering (nonnesting) areas 

offering an abundant and readily 

available food supply with suitable 

night roosts. Night roosts typically offer 

isolation and thermal protection from 

winds. Carrion and easily scavenged 

prey provide important sources of 

winter food in terrestrial habitats far 

from open water. 

The first major decline in the bald 

eagle population probably began in the 

mid to late 1800s. Widespread shooting 

for feathers and trophies led to 

extirpation of eagles in some areas. 

Shooting also reduced part of the bald 

eagle’s prey base. Big game animals like 

bison, which were seasonally important 

to eagles as carrion, were decimated. 

Hunters also reduced the numbers of 

waterfowl, shorebirds, and small 

mammals. Ranchers used carrion treated 

with strychnine, thallium sulfate, and 

other poisons as bait to kill livestock 

predators and ultimately killed many 

eagles as well. These were the major 

factors, in addition to loss of nesting 

habitat from forest clearing and 

development, which contributed to a 

reduction in bald eagle numbers 

through the 1940s. In 1940, Congress 

passed the Bald Eagle Protection Act (16 

U.S.C. 668–668d). This law prohibits 

the take, possession, sale, purchase, 

barter, or offer to sell, purchase or 

barter, transport, export or import, of 

any bald eagle, alive or dead, including 

any part, nest, or egg, unless allowed by 

permit (16 U.S.C. 668(a)). ‘‘Take’’ 

includes pursue, shoot, shoot at, poison, 

wound, kill, capture, trap, collect, 

molest or disturb (16 U.S.C. 668c; 50 

CFR 22.3). The Bald Eagle Protection 

Act and increased public awareness of 

the bald eagle’s status resulted in partial 

recovery or at least a slower rate of 

decline of the species in most areas of 

the country. 

In the late 1940s, the use of dichlorodiphenyltrichloroethane (DDT) and 

other organochlorine compounds 

became widespread. Initially, DDT was 

sprayed extensively along coastal and 

other wetland areas to control 

mosquitoes (Carson 1962, pp. 28–29, 

45–55). Later farmers used it as a 

general crop insecticide. As DDT 

accumulated in individual bald eagles 

from ingesting prey containing DDT and 

its metabolites, reproductive success 

plummeted. In the late 1960s and early 

1970s, it was determined that 

dichlorophenyl-dichloroethylene (DDE), 

the principal breakdown product of 

DDT, accumulated in the fatty tissues of 

adult female bald eagles. DDE impaired 

calcium release necessary for normal 

eggshell formation, resulting in thin 

shells and reproductive failure. 

In response to this decline, the 

Secretary of the Interior, on March 11, 

1967 (32 FR 4001), listed bald eagles 

south of the 40th parallel as endangered 

under the Endangered Species 

Preservation Act of 1966 (16 U.S.C. 

668aa–668cc). Bald eagles north of this 

line were not included in that action 

primarily because the Alaskan and 

Canadian populations were not 

considered endangered in 1967. On 

December 31, 1972, the Environmental 

Protection Agency banned the use of 

DDT in the United States. The following 

year, Congress passed the Endangered 

Species Act of 1973 (16 U.S.C. 1531– 

1544). 

Nationwide bald eagle surveys, 

conducted in 1973 and 1974 by the 

Service, other cooperating agencies, and 

conservation organizations, revealed 

that the eagle population throughout the 

lower 48 States was declining. We 

responded in 1978 by listing the bald 

eagle throughout the lower 48 States as 

endangered except in Michigan, 

Minnesota, Wisconsin, Washington, and 

Oregon, where it was designated as 

threatened (43 FR 6233, February 14, 

1978). 

To facilitate the recovery of the bald 

eagle and the ecosystems upon which it 

depends, we divided the lower 48 States 

into five recovery regions. Separate 

recovery teams composed of experts in 

each geographic area prepared recovery 

plans for their region. The teams 

established goals for recovery and 

identified tasks to achieve those goals. 

Coordination meetings were held 

regularly among the five teams to 

exchange data and other information. 

We used these five recovery plans to 

provide guidance to the Service, States, 

and other partners on methods to 

minimize and reduce the threats to the 

bald eagle and to provide measurable 

criteria that would be used to help 

determine when the threats to the bald 

eagle had been reduced so that the bald 

eagle could be removed from the 

Federal List of Endangered and 

Threatened Wildlife and Plants. 

Recovery plans in general are not 

regulatory documents and are instead 

intended to provide a guide on how to 

achieve recovery. There are many paths 

to accomplishing recovery of a species. 


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The main goal is to remove the threats 

to a species, which may occur without 

meeting all recovery criteria contained 

in a recovery plan. For example, one or 

more criteria may have been exceeded 

while other criteria may not have been 

accomplished. In that instance, the 

Service may judge that, overall, the 

threats have been reduced sufficiently, 

and the species is robust enough, to 

reclassify the species from endangered 

to threatened or perhaps to delist the 

species. In other cases, recovery 

opportunities may be recognized that 

were not known at the time the recovery 

plan was finalized. Achievement of 

these opportunities may be counted as 

progress toward recovery in lieu of 

methods identified in the recovery plan. 

Likewise, we may learn information 

about the species that was not known at 

the time the recovery plan was 

finalized. The new information may 

change the extent that criteria need to be 

met for recognizing recovery of the 

species. Overall, recovery of species is 

a dynamic process requiring adaptive 

management, and judging the degree of 

recovery of a species is also an adaptive 

management process that may, or may 

not, fully follow the guidance provided 

in a recovery plan. 

Recovery of the bald eagle has been a 

dynamic process. During the recovery 

implementation process the Service 

used new information as it became 

available, to help determine whether 

recovery was on track. For instance, 

after the bald eagle was downlisted in 

1995, the Southeastern Recovery Plan 

did not have specific delisting goals, 

and the Service used the recovery team 

to help determine the appropriate goal. 

This new delisting goal, developed by a 

team of individuals with bald eagle 

expertise, was the best guidance 

available to the Service for use in 

determining whether threats had been 

removed and whether to move forward 

with delisting was appropriate. 

Between 1990 and 2000, the bald 

eagle population had a national average 

productivity of at least one fledgling per 

nesting pair per year. As a result, the 

bald eagle’s nesting population 

increased at a rate of about eight percent 

per year during this time period. Since 

1963, when the Audubon Society 

estimated that there were 487 nesting 

pairs, bald eagle breeding in the lower 

48 States has expanded to more than 

9,789 nesting pairs (Service 1995, p. 

36001; Service 1999, p. 36457). By 2007, 

the bald eagles bred in each of the lower 

48 States, with the greatest number of 

breeding pairs occurring in Minnesota 

(1,313), Florida (1,133), Wisconsin 

(1,065), and Washington (848) (Service 

2007, p. 37349). 

Regional bald eagle populations in the 

Northwest, Great Lakes, Chesapeake 

Bay, and Florida have increased fivefold from the late 1970s to the late 

1990s. Bald eagles are now repopulating 

areas throughout much of the species’ 

historical range that were unoccupied 

only a few years ago (64 FR 36454; July 

6, 1999). The nationwide recovery of the 

bald eagle is due in part to the reduction 

in levels of persistent organochlorine 

pesticides (such as DDT) and habitat 

protection and management actions. 

Historical and Current Status of the 

Sonoran Desert Area Population 

Below we discuss the status of eagles 

in the Sonoran Desert Area population 

and in the States surrounding the 

Sonoran Desert Area population because 

it provides a context for our evaluation 

of whether the Sonoran Desert Area is 

a distinct population segment of bald 

eagles. As described above, the Sonoran 

Desert Area refers to all Sonoran Desert 

bald eagle territories within Arizona, the 

Copper Basin breeding area along the 

Colorado River just into California, and 

the territories of interior Sonora, 

Mexico. Bald eagles in Baja California 

are not included in our definition of the 

Sonoran Desert Area population because 

(1) they are associated with a marine, 

rather than inland, environment 

(Figure 1), (2) there is no documentation 

of Baja bald eagles interchanging with 

those in the Sonoran Desert Area, and 

(3) currently extant nests in Baja are 

limited to the Magdalena Bay region 

along the coast of the Pacific Ocean 

(Arnaud et al. 2001, p. 136; and King 

2006, p. 4), in a coastal, rather than 

inland, climate. 

Arizona 

Hunt et al. (1992, pp. A11–A12) 

summarized the earliest records from 

the literature for bald eagles in Arizona. 

Coues noted bald eagles in the vicinity 

of Fort Whipple (now Prescott) in 1866, 

and Henshaw reported bald eagles south 

of Fort Apache in 1875. Bent (1937, pp. 

321–333) reported breeding eagles at 

Fort Whipple in 1866 and on the Salt 

River Bird Reservation (since inundated 

by Roosevelt Lake) in 1911. Breeding 

eagle information was also recorded in 

1890 near Stoneman Lake by S.A. 

Mearns. Additionally, there are reports 

of bald eagles along rivers in the White 

Mountains from 1937, and reports of 

nesting bald eagles along the Salt and 

Verde Rivers as early as 1930. Hunt et 

al. (1992, pp. D41–D46, D291–D326, 

Figures D4.0–1, D5.0–1, F3, F4, and F5) 

determined from reports and personal 

communications dating back to 1866 

that historically there were 28 known 

breeding areas, 22 known and probable 

nest sites, and at least 60 unverified 

reports of possible nests/nest sites and 

unverified reports of bald eagles located 

across the State of Arizona. Many of the 

60 possible nests/nest sites reported by 

Hunt et al. (1992) could be a collection 

of nests belonging to the same breeding 

territory. These reported locations 

ranged to the boundaries of the State 

from the Grand Canyon near Lake 

Powell, to the lower Colorado River 

where it separates Arizona and 

California, to the upper San Pedro River 

near the international border with 

Mexico, and east near the boundary 

with New Mexico (Hunt et al. 1992, 

Figures D4.0–1, D5.0–1, F3, F4, and F5). 

More recent survey and monitoring 

efforts have increased our knowledge of 

bald eagle distribution in Arizona. The 

number of known breeding areas in 

Arizona in 1971 was 3; the number 

known in 2009 is 59. The number of 

bald eagle pairs occupying these sites 

increased from 3 in 1971 to 48 in 2009. 

The number of young hatched increased 

from a low of zero in 1972 to a high of 

55 in 2006 (Driscoll et al. 2006, pp. 

48–49; McCarty and Johnson 2009, p. 8, 

in draft). Productivity has also changed 

at the bald eagle breeding areas since 

the 1970s. Between 1975 and 1984, 

average annual productivity was 0.95 

young per occupied breeding area. 

Between 1987 and 2005, average annual 

productivity was 0.78 young per 

occupied breeding area (derived from 

Table 7, pp. 48–50 in Driscoll et al. 

2006). (These data take into account 

productivity for breeding areas 

throughout Arizona, and are not 

restricted to the Sonoran Desert 

population of bald eagles evaluated 

under the petition.) 

Hunt et al. (1992, p. A155) conclude 

that it is likely that bald eagles nested 

on rivers throughout the Southwest in 

more pristine times, as reports on the 

nature of river systems and the 

assemblage of prey fishes both seem 

conducive to nesting success and 

suggest ‘‘richer and more extensive 

habitat in the lower desert’’ than would 

have been available on the Mogollon 

Plateau, where bald eagles are known to 

have occurred historically. Recent 

reoccupation of some of these historical 

breeding areas by bald eagles lends 

credibility to these reports. We 

evaluated a subset of the Allison et al. 

(2008, pp. 17–18) data to determine the 

status of 43 breeding areas within the 

Sonoran Desert Area of Arizona and 

concluded that 16 (37 percent) were 

pioneer breeding areas, or occupied for 

the first time. An additional 27 (63 

percent) were either reoccupied, 

meaning they were known to have been 

occupied in the past, then vacated, and 


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subsequently reoccupied, or are 

considered to have been existing before 

their discovery (Allison et al. 2008, pp. 

15–16). 

The Salt River Pima-Maricopa Indian 

Community states that the O’odham 

have inhabited the Sonoran Desert and 

have known eagles since ‘‘time 

immemorial’’ (Anton and Garcia-Lewis 

2009, p. 1). Although anthropologists 

debate what this means, at least one 

noted archaeologist has documented 

detailed evidence of cultural remains in 

the nearby Pinacate area that date back 

more than 40,000 years (Hayden and 

Dykinga 1988, p. XIV). A local, informal 

consensus of 10,000 years is less 

controversial (Toupal 2003, p. 11). Bald 

eagles have been documented 

historically within the culture of the 

Four Southern Tribes of Arizona, which 

includes the Salt River Pima-Maricopa 

Indian Community, Ak-Chin Indian 

Community, Gila River Indian 

Community, and Tohono O’odham 

Nation (Anton and Garcia-Lewis 2009, 

p. 2). Because eagles are considered to 

have equal or greater standing to 

humans, eagle burials were carried out 

identical to human burial practices 

(Anton and Garcia-Lewis 2009, p. 2), 

and bald eagle burials have been 

recovered from archaeological sites 

ancestral to the O’odham culture. In 

addition, eagles are extremely 

prominent in the O’odham song culture 

(Anton and Garcia-Lewis 2009, p. 2). A 

paired set of songs recorded by 

Underhill (1938, p. 109) for a Tohono 

O’odham eagle purification ceremony 

recognized the bald eagle as the ‘‘whiteheaded eagle.’’ 

More recent evidence exists to 

demonstrate the importance and use of 

bald eagles in Apache culture. 

Herrington et al. (1939, pp. 13–15) 

noted the use of eagle feathers in 

religious practices and ceremonial 

dances. The Apache Tribes have 

documented numerous artifacts that 

were collected from the Tribes at 

Cibecue and East Fork/Whiteriver on 

the White Mountain Apache 

Reservation and on the San Carlos 

Reservation between 1901 and 1945. 

These Tribes note that these artifacts 

were made, in part, with eagle feathers, 

and include hats or caps; shields; 

medicine rings, shirts, and strings; 

amulets; war bonnets; armbands; hair 

ornaments; and wooden figurines and 

crosses. The Tribes note that these 

ceremonial items are of deep historical 

and ongoing importance, such that they 

are actively pursuing their return from 

the museums to the Tribes. The 

existence of these items demonstrates 

the use of eagle feathers by the Tribes 

for at least the last 100 years (Apache 

Tribes 2009, Tabs 6–10). 

Traditional ecological knowledge 

from the Apache Tribes report more 

breeding bald eagles 150 years ago than 

are present today. Specifically, Tribal 

representatives note that many areas 

that were considered nesting sites on 

the San Carlos Apache Reservation such 

as Warm Springs Canyon, Black River 

Canyon, and Salt Creek Canyon no 

longer contain active bald eagle nests. 

Bald eagles are no longer found at four 

out of seven areas that have Apache 

place-names that reference bald eagles 

(Lupe et al. pers. comm. 2008, p. 4). The 

traditional ecological knowledge shared 

by the Tribes at a July 2, 2008, meeting 

indicate that more bald eagles were 

observed below Coolidge Dam and at 

Talkalai Lake than currently exist. 

Nevada 

There are few historical or current 

breeding records for the State of Nevada. 

The lone historical record describes 

bald eagles that nested in a cave on an 

island at Pyramid Lake in northwestern 

Washoe County in northwestern Nevada 

in 1866 (Service 1986, p. 7; Detrich 

1986, p. 11; S. Abele, Service, pers. 

comm. 2008a; 2008b). Over 100 years 

later, the next verified nesting record 

occurred in 1985 along Salmon Falls 

Creek in Elko County in northeastern 

Nevada near the Idaho border. More 

modern nesting records are limited to 

approximately five breeding sites 

associated with human-made water 

impoundments. Reproductive 

performance and persistence of bald 

eagle pairs in Nevada has been varied. 

No breeding has been observed at the 

Salmon Falls site since 1985. 

Colorado 

According to the Northern Bald Eagle 

Recovery Plan, bald eagles in Colorado 

historically nested in the mountainous 

regions up to 10,000 ft (3,048 m). 

Successful nesting records exist for 

nests found in southwestern and westcentral Colorado. Bald eagles were 

considered common residents in the 

1940s and 1950s in and around Rocky 

Mountain National Park (Service 1983, 

p. 12). For southwestern Colorado, there 

were no verified records of nesting bald 

eagles in the 1960s (Bailey and Niedrach 

1965 in Stahlecker and Brady 2004, p. 

2). The first confirmed record for 

southwestern Colorado occurred in 1974 

at Electra Lake (Winternitz 1998 in 

Stahlecker and Brady 2004, p. 2). In 

1974, the Colorado Division of Wildlife 

reported that only a single nesting pair 

was known (Colorado Division of 

Wildlife 2008, p. 1). However, by 1981, 

there were five known occupied bald 

eagle territories in the State of Colorado 

(Service 1983, p. 23), and from the early 

1980s to 2008, the known bald eagle 

population increased to nearly 80 

territories, of which 60 are currently 

known to be active. Concentrations of 

breeding eagles are found east of the 

Continental Divide within the South 

Platte River watershed, on the Yampa 

River, on the White River, and on the 

Colorado River. Greater than 40 

territories are monitored annually, with 

near 70 percent nest success, 1.19 young 

fledged per occupied site, and 1.72 

young fledged per successful site 

(Colorado Division of Wildlife 2008, p. 

1). 

New Mexico 

Available information indicates there 

was no specific, first-hand information 

on bald eagles nesting in New Mexico 

prior to 1979. Unverified reports (Bailey 

1928, p. 180; Ligon 1961, p. 75) suggest 

one or two pairs may have nested in 

southwestern New Mexico, on the upper 

Gila River and possibly the San 

Francisco River, prior to 1928. These 

second-hand reports lacked specifics 

and may have referred to other species 

(Williams 2000, p. 1). 

Since completion of the 1982 

Recovery Plan, seven bald eagle 

territories have been discovered, five in 

northern New Mexico in Colfax and Rio 

Arriba Counties and two in southwest 

New Mexico in Sierra and Catron 

Counties. Four have been recently 

occupied and productivity has been fair 

with young produced in at least 6 to 15 

years, depending on the territory (H. 

Walker, New Mexico Department of 

Game and Fish, pers. comm. 2008). 

Southern California 

In southern California, historical bald 

eagle records are known from the 

Channel Islands and mainland counties 

along the Pacific Ocean (Detrich 1986, 

pp. 9–27). Prior to 1900, three bald eagle 

territory records were known (Detrich 

1986, pp. 10–13). From 1900 to 1940, 

reports of 24 to 60 nest sites existed on 

islands off the coast of California, and 

are believed to have been extirpated 

from the islands soon after 1958 

(Detrich 1986, pp. 18, 24). In inland 

areas in southern California, at least 

eight bald eagle pairs were known from 

Santa Barbara, Ventura, Los Angeles, 

Orange, and San Diego counties 

between 1900 and 1940, with 

indications of presence prior to this 

timeframe (Detrich 1986, pp. 13–19). By 

1981, largely due to adverse changes to 

bald eagle habitat and the effects of the 

pesticide DDT on reproduction, no 

breeding eagles were detected on the 

southern California mainland (Detrich 


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1986, pp. 32, 33, 36, 39; California 

Department of Fish and Game 2008, p. 

2). 

Beginning in 1980, bald eagles were 

translocated to Santa Catalina Island as 

chicks or eggs from wild nests on the 

mainland, or from captive breeding. 

Pairs of bald eagles have been breeding 

on the island since 1987. In a 

subsequent relocation effort between 

1987 and 1995 in the central coast 

mountains of Monterey Bay, 66 eaglets 

were translocated and released. A 

nesting pair first formed from those 

releases in 1993, and there are currently 

three nesting pairs (California 

Department of Fish and Game 2008, pp. 

2–3). Releases of birds occurred through 

2000, with no releases conducted 

between 2002 and 2008 (Ventana 

Wildlife Society 2009, p. 1). Currently, 

there are approximately six pairs of bald 

eagles on Catalina Island, with an 

additional three pairs at Santa Cruz 

Island, and one pair at Santa Rosa 

Island. There are approximately 35 to 40 

bald eagles around the Northern 

Channel Islands, and another 20 birds 

around Catalina, for a total of 

approximately 60 birds among the 

Channel Islands (A. Little, pers. comm. 

2008). 

Presently, mainland southern 

California nesting bald eagles occur at 

inland isolated manmade reservoirs. 

Bald eagle breeding sites can be found 

in northwestern San Luis Obispo 

County (San Antonio and Nacimiento 

Lakes), central Santa Barbara County 

(Lake Cachuma), southwestern San 

Bernardino County (Silverwood Lake), 

extreme eastern San Bernardino County 

near the Colorado River (Copper Basin 

Lake), southwestern Riverside County 

(Hemet and Skinner lakes), and central 

San Diego County (Lake Henshaw) 

(AGFD 2008, California Department of 

Fish and Game 2008, pp. 2–3; Driscoll 

and Mesta in prep. 2005, p. 110; 

Ventana Wildlife Society 2008, p. 1). 

Nesting attempts at Silverwood and 

Hemet Lakes are considered sporadic 

(Service 2005, p. 110). At Skinner Lake, 

reproduction efforts in the mid-1990s 

were affected by DDT, and the nest area 

subsequently burned down (Driscoll 

and Mesta in prep. 2005; AGFD 2008). 

Nest sites in northwestern San Luis 

Obispo County appear to be very 

productive, producing eaglets in all but 

one year from 1993 to 2006 (Ventana 

Wildlife Society 2008, p. 7). For 2001 to 

2008, two or three young have fledged 

annually from the Copper Basin 

breeding area, with the exception of 

2004 when the nest was blown down 

(M. Melanson, Metropolitan Water 

District of Southern California, pers. 

comm. 2006a, 2007, 2008). The blue 

aluminum leg bands of one of the adult 

bald eagles at the Copper Basin site 

indicate that the bird likely originated 

in Arizona (M. Melanson, Metropolitan 

Water District of Southern California, 

pers. comm. 2006b). 

Utah 

Bald eagles were recorded as ‘‘more or 

less frequent’’ by Allen in 1871 (p. 164) 

in the vicinity of Ogden in northern 

Utah. There are seven historical records 

for Utah between 1875 and 1928, with 

five records of nesting bald eagles, and 

two other records of nonbreeding bald 

eagle observations, all located between 

Great Salt Lake and Utah Lake in 

northern Utah. In 1967, a nest was 

found to the south in Wayne County at 

Bicknell, and in 1972, an additional nest 

was located at Joes Valley Reservoir in 

San Pete County in central Utah, but it 

has since fallen. Additional records 

from the 1970s were of nests along the 

Colorado River at Westwater Canyon in 

1975, and at the head of Westwater 

Canyon between 1973 and 1977. 

Beginning in 1983, nesting attempts 

occurred at three nesting territories in 

southeast Utah. Two of the territories 

were along the Colorado River near the 

eastern border of Utah, with the third 

near Castle Dale in the center of the 

State (Boschen 1995, pp. 7–8). Three 

known nest sites (Cisco, Bitter Creek, 

and Castle Dale) were reported 

following survey work completed in 

1994. These three nest sites produced an 

average of approximately 1.4 nestlings, 

with 1.05 successfully fledged between 

1983 and 1994 (Boschen 1995, p. 103). 

Approximately 11 breeding areas were 

known, considered active, and 

monitored between 1983 and 2005 

(Darnell, Service, pers. comm. 2008). 

West Texas 

Historically, there were five nesting 

records for bald eagles west of the 100th 

Meridian in Texas. Lloyd (1887, p. 189) 

reported nesting in Tom Green and 

Concho counties in 1886. Oberholser 

(1974, p. 246) and Boal (2006, p. 46) 

reported eggs collected in Potter County 

near Amarillo by E.W. Gates in 1916. 

Oberholser (1974, in Service 1982, p. 8) 

additionally reported eggs collected by 

Smissen in 1890 in Scurry County south 

of Lubbock. Oberholser also reported an 

undated sight record of breeding eagles 

in Armstrong County near Amarillo. 

Kirby (pers. comm., in Service 1982) 

reported an active nest in nearby 

Wheeler County in 1938, and indicated 

it had been active for approximately 20 

years. Throughout the 1980s and early 

1990s there were no known breeding 

bald eagles in western Texas (Mabie et 

al. 1994, p. 215; Service 1982, p. 9). In 

2004 and 2005, two adult bald eagles 

and a nestling were observed at a nest 

in the southern Great Plains of the Texas 

Panhandle. One young was produced in 

2004, and two in 2005. No leg bands 

were readily observable on the adult 

eagles (Boal et al. 2006, pp. 246–247). 

Sonora, Mexico 

Bald eagle territories were first 

recorded in Sonora along the Rio Yaqui 

drainage in 1986 (Brown et al. 1986, pp. 

7–14). Since that time, a total of seven 

bald eagle breeding areas were verified 

(Brown et al. 1986, pp. 7–14; Brown et 

al. 1987b, pp. 1–2, 1987b, p. 279; Brown 

1988, p. 30; Brown and Olivera 1988, 

pp. 13–16; Brown et al. 1989, pp. 13– 

15; Brown et al. 1990, pp. 7, 9; Mesta 

et al. 1993, pp. 8–12; Russell and 

Monson 1998, pp. 62–63; Driscoll and 

Mesta 2005 in prep., pp. 78–90). Four of 

these bald eagle breeding areas have 

remained occupied (Driscoll and Mesta, 

in prep., pp. 78–90). However, 

reproductive performance of these nests 

has been relatively poor. Only a single 

nestling was recorded fledging in 2000 

and 2001, and no successful nests were 

observed in 1999, 2002, and 2005 

(Driscoll and Mesta in prep., p. 43). In 

2008, no occupancy was detected at 

bald eagle territories (R. Mesta, Service, 

pers. comm. 2008). A bald eagle pair 

was observed in 2009; however, the 

previously used cliff nest is gone, and 

a new nest was not confirmed. Illegal 

drug activity in the area has increased 

human presence, making survey work 

difficult to accomplish. The area is also 

affected by extensive water 

withdrawals, and drought and dam 

operations, leaving the future of this site 

uncertain (R. Mesta, Service, pers. 

comm. 2009). 

Defining a Species Under the Act 

Section 3(16) of the Act defines 

‘‘species’’ to include ‘‘any species or 

subspecies of fish and wildlife or plants, 

and any distinct population segment of 

any species of vertebrate fish or wildlife 

which interbreeds when mature’’ (16 

U.S.C. 1532(16)). To interpret and 

implement the distinct vertebrate 

population segment provisions of the 

Act and congressional guidance, the 

Service and the National Marine 

Fisheries Service (now the National 

Oceanic and Atmospheric 

Administration—Fisheries Service), 

published the Policy Regarding the 

Recognition of Distinct Vertebrate 

Population Segments (DPS Policy) in 

the Federal Register on February 7, 

1996 (61 FR 4722). The DPS Policy sets 

forth a three-step process: First, the 

Policy requires the Service to determine 

that a vertebrate population is discrete 


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and, if the population is discrete, then 

a determination is made as to whether 

the population is significant. Lastly, if 

the population is determined to be both 

discrete and significant then the Policy 

requires a conservation-status 

determination to determine if the DPS is 

an endangered or threatened species. 

Distinct Vertebrate Population Segment 

Analysis 

In accordance with our DPS Policy, 

this section details our analysis of 

whether the vertebrate population 

segment under consideration for listing 

may qualify as a DPS. Specifically, we 

determine (1) the population segment’s 

discreteness from the remainder of the 

species to which it belongs and (2) the 

significance of the population segment 

to the species to which it belongs. 

Discreteness refers to the ability to 

delineate a population segment from 

other members of a taxon based on 

either (1) physical, physiological, 

ecological, or behavioral factors, or (2) 

international boundaries that result in 

significant differences in control of 

exploitation, management, or habitat 

conservation status, or regulatory 

mechanisms that are significant in light 

of section 4(a)(1)(B) of the Act. 

Under our DPS Policy, if we have 

determined that a population segment is 

discrete under one or more of the 

discreteness conditions, we consider its 

significance to the larger taxon to which 

it belongs in light of congressional 

guidance (see Senate Report 151, 96th 

Congress, 1st Session) that the authority 

to list DPSs be used ‘‘sparingly’’ while 

encouraging the conservation of genetic 

diversity. In carrying out this 

examination, we consider available 

scientific evidence of the population’s 

importance to the taxon to which it 

belongs. This consideration may 

include, but is not limited to the 

following: (1) The persistence of the 

population segment in an ecological 

setting that is unique or unusual for the 

taxon; (2) evidence that loss of the 

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 of its 

historic range; and (4) evidence that the 

discrete population segment differs 

markedly from other populations of the 

species in its genetic characteristics. 

The first step in our DPS analysis was 

to identify populations of the Sonoran 

Desert Area population to evaluate. The 

petition from CBD, the Maricopa 

Audubon Society, and the Arizona 

Audubon Council requested that the 

‘‘Southwestern desert nesting bald eagle 

population’’ be classified as a DPS, that 

this DPS be reclassified from a 

threatened species to an endangered 

species, and that we concurrently 

designate critical habitat for the DPS 

under the Act. 

Determination of the Area for Analysis 

The March 6, 2008, court order 

directed the Service to conduct a status 

review of the ‘‘Desert bald eagle 

population.’’ The population referenced 

in the court order consists of those bald 

eagles in the Sonoran Desert of the 

southwest that reside in central Arizona 

and northwestern Mexico. While we 

had specific clarification from the 

petitioners with respect to elevational 

boundaries, bald eagle breeding areas, 

the Upper and Lower Sonoran Life 

Zones, and the State of Arizona, they 

provided ambiguous clarification with 

respect to the boundaries of ‘‘central 

Arizona’’ and which transition areas 

outside of the Upper and Lower 

Sonoran Life Zones to include. Because 

of these ambiguities and lack of a 

specific map in the petition, we were 

left to interpret them, primarily at the 

perimeters of the boundary. 

In responding to the court order, we 

published a rule on May 1, 2008, 

reinstating threatened status under the 

Act to the bald eagle in the Sonoran 

Desert Area of Central Arizona in eight 

Arizona counties: (1) Yavapai, Gila, 

Graham, Pinal, and Maricopa Counties 

in their entirety; and (2) southern 

Mohave County (that portion south and 

east of the centerline of Interstate 

Highway 40 and east of Arizona 

Highway 95), eastern LaPaz County (that 

portion east of the centerline of U.S. and 

Arizona Highways 95), and northern 

Yuma County (that portion east of the 

centerline of U.S. Highway 95 and north 

of the centerline of Interstate Highway 

8). We limited the reinstatement of 

threatened status to these areas because 

Sonoran Desert bald eagles were only 

listed under the Act in Arizona (and not 

in Mexico) at the time of the petition. 

Therefore, the court’s order enjoining 

our final delisting decision applied only 

to those eagles that reside in the 

Sonoran Desert of central Arizona. 

For this status review, we revisited 

the issue of defining the potential DPS 

based on a more in-depth review of 

information received from the public, 

Tribes, and information in our files. We 

determined that an appropriate 

delineation for this analysis includes all 

Sonoran Desert bald eagle territories 

within Arizona, the Copper Basin 

breeding area along the Colorado River 

just into California, and the territories of 

Sonora, Mexico. This expanded 

boundary was developed using 

vegetation community boundaries, 

elevation, and breeding bald eagle 

movement. This interpretation 

combines geographic proximity and 

recognized Sonoran Desert vegetation 

and transition life zones. We 

determined the transition areas based on 

our knowledge of their proximity to the 

Sonoran Desert itself, excluding 

territories more properly classified as 

montane or grassland habitat. Bald 

eagles in Baja California, Mexico, occur 

in an area where the Sonoran Desert 

vegetation community abuts a coastal 

environment. We excluded bald eagles 

in this area because they depend on 

marine resources rather than inland 

fisheries. We based delineation of the 

potential DPS on the best available 

scientific information, including the 

parameters provided by CBD (i.e., bald 

eagle territories, elevation, life zones, 

and transition areas), and the resulting 

expanded boundary includes known 

bald eagle breeding areas within the 

Sonoran Desert vegetation community 

and transition areas, as defined by 

Brown (1994, pp. 181–221), except Baja 

California. 

As noted above, we included Sonora, 

Mexico, in the potential DPS because 

both areas have the same vegetation and 

climate. Bald eagles in Sonora use 

Sonoran Desert and transition 

vegetation communities as do bald 

eagles in the Sonoran Desert areas of 

Arizona and southern California. In 

addition, breeding season chronology in 

both areas appears to be similar 

(Driscoll et al. 2005 in prep., pp. 31–32), 

occurring between December and June. 

Bald eagles in Sonora also nest in 

riparian trees and cliffs, as they do in 

Arizona (Driscoll et al. 2005 in prep., p. 

31). 

When based strictly on vegetation or 

elevation lines, the expanded boundary 

is irregular and complex, and would be 

difficult to interpret. For this reason, we 

delineated the boundary with more 

easily identifiable road, county, and 

State lines. 

Discreteness 

Under the DPS Policy, a population 

segment of a vertebrate taxon may be 

considered discrete if it satisfies either 

one of the following 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. 

(2) It is delimited by international 

governmental boundaries within which 

differences in control of exploitation, 


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management of habitat, conservation 

status, or regulatory mechanisms exist 

that are significant in light of section 

4(a)(1)(D) of the Act. 

Boundaries of the Potential DPS 

Many terms have been used in 

describing the bald eagles that occupy 

the desert southwest, and we identify 

here the geographic area covered by the 

various terms. At the broadest 

geographic scale, bald eagles were 

managed under the Southwest Bald 

Eagle Recovery Region, which 

encompassed Oklahoma, Texas west of 

the 100th meridian, all of New Mexico 

and Arizona, and those portions of 

southeastern California that border the 

lower Colorado River. Bald eagles 

within this area were called 

‘‘southwestern bald eagles’’ (Service 

1982, p. 1). Much of the data used in the 

development of the potential DPS 

boundary for this discreteness analysis 

came from those eagles within the 

boundaries of the State of Arizona. The 

petition that initiated this 12-month 

status review referred to the 

Southwestern Desert Nesting Bald Eagle 

Population, which included those eagles 

that breed predominantly in the upper 

and lower Sonoran life zone habitat. In 

our August 30, 2006, analysis at the 90- 

day petition finding stage (71 FR 51549), 

we evaluated ‘‘Sonoran Desert bald 

eagles,’’ which included those bald 

eagles in the Sonoran Desert of central 

Arizona and northwest Mexico. 

In analyzing the potential DPS under 

this 12-month status review, we 

considered habitat use by bald eagles 

breeding in the Southwest, vegetation 

communities in which breeding areas 

occur, and elevation levels at which 

breeding areas occur, as we did at the 

90-day petition finding stage. However, 

we have reevaluated all potential areas 

including those considered in the 90- 

day finding to include any areas that 

meet the criteria described below. As a 

result, in this review, we did not restrict 

the boundary to the State of Arizona and 

have expanded the area covered by our 

previous analysis to include portions of 

southeastern California along the 

Colorado River, Arizona, and Sonora, 

Mexico. We now refer to this expanded 

potential DPS area as the Sonoran 

Desert Area population, which replaces 

the term ‘‘Sonoran Desert Area of central 

Arizona,’’ as described in our May 1, 

2008, Federal Register rule (73 FR 

23966) to list the Sonoran Desert bald 

eagle as threatened. 

To determine which areas should be 

included within the expanded boundary 

for the Sonoran Desert Area, we 

considered three factors: (1) The 

Sonoran Desert vegetation community 

(Brown 1994, pp. 180–221; Brown and 

Lowe 1994, map), (2) an elevational 

range for known breeding areas within 

the Sonoran Desert (excluding Baja 

California), and (3) movement patterns 

of breeding bald eagles both into and 

out of the Sonoran Desert Area. We 

included within the boundary portions 

of the Sonoran Desert, including its 

subdivisions and ‘‘transition areas.’’ 

Subdivisions of the Sonoran Desert 

include the Lower Colorado River 

Valley, Arizona Upland, Vizcaino, 

Central Gulf Coast, Plains of Sonora, 

and Magdalena (Brown 1994, pp. 190– 

221). Transition areas are those 

vegetation communities adjacent to the 

Sonoran Desert community. Brown 

(1994, p. 181) includes as transition 

areas semidesert grasslands, Sinaloan 

thornscrub, and chaparral. The majority 

of the breeding areas within the 

boundary occur in the Arizona Upland 

Subdivision of the Sonoran Desert. 

Exceptions include those breeding areas 

in the transition communities (where 14 

of 61 breeding areas are located) of 

Interior Chaparral, Plains & Great Basin 

Grassland, Semidesert Grassland, and 

Sinaloan Thornscrub (Brown 1994). 

These communities are most often 

adjacent to the Arizona Upland 

Subdivision of the Sonoran Desert, 

where bald eagles in these areas forage 

at least partially within the desertscrub. 

We also based the boundary on those 

portions of the Southwest within the 

elevational range of 984 to 5,643 ft (300 

to 1,720 m). This elevational range 

encompasses all known bald eagle 

breeding areas within the Sonoran 

Desert in the United States and Sonora, 

Mexico. Using Geographic Information 

Systems, the appropriate elevational 

ranges were overlapped with the 

Sonoran Desert vegetation community 

to determine where both criteria were 

met. 

We also considered information on 

movement of bald eagles into and out of 

the Sonoran Desert, as determined 

through banding and monitoring 

information. Specifically, we included 

within the boundary those bald eagles 

known to originate in or breed in the 

Sonoran Desert and transition areas, 

excluding Baja California. The banding 

and monitoring information used to 

determine eagles originating or breeding 

in the Sonoran Desert Area is described 

in detail below. 

Figure 1 below illustrates the 

boundary developed based on 

vegetation community, elevation, and 

breeding bald eagle movement. The 

boundary was modified from following 

strictly elevational or vegetation lines to 

follow more easily identifiable road, 

county, and State lines. 

BILLING CODE 4310–55–P 


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BILLING CODE 4310–55–C 

The northern perimeter of the 

expanded potential DPS boundary in 

Arizona is the same as the potential DPS 

boundary that we used in our May 1, 

2008, Federal Register notice (73 FR 

23966) to list the Sonoran Desert bald 

eagle DPS as threatened. This boundary 

follows the southern edges of Coconino, 

Navajo, and portions of Apache 

Counties. It follows the Graham County 

line south on the east side until it 

reaches the Cochise County boundary. 

On the west, the boundary drops 

south along the Mohave-Yavapai 

boundary until it reaches Interstate 40. 

The discreteness boundary then follows 

Interstate 40 west until its intersection 

with the State boundary. It continues 

west 5 miles (mi) (8 kilometers (km)) 

and then south along a line drawn 5 mi 

(8 km) west of and parallel to the 

Colorado River until it reaches Highway 

2 in Sonora, Mexico. 

The southern boundary of the 

expanded potential DPS follows 

Highway 2 in Mexico east until its 

intersection with Highway 15. It follows 

Highway 15 until its intersection with 

Highway 16. The southern boundary 

continues along Highway 16 until it 

reaches the State boundary between 

Sonora and Chihuahua. The eastern 

boundary of the expanded potential DPS 

follows the State line between Sonora 

and Chihuahua north until it reaches 

the international boundary between the 

United States and Mexico at New 

Mexico, and continues west to the State 

boundary between Arizona and New 

Mexico. The eastern boundary then 

continues north along Cochise County, 

turning slightly west along the northern 

edge of Cochise County before rejoining 

the northern perimeter. 


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Bald eagles within the boundary that 

constitute the expanded potential DPS 

include those that occur within the 

appropriate vegetation communities and 

elevational range. The breeding area 

located in southeastern California is 

within the Lower Colorado River 

subdivision of the Sonoran Desert. In 

addition, the bald eagles at that breeding 

area originated at the Horseshoe 

Breeding Area in Arizona. We have 

included Sonora, Mexico, within the 

potential DPS because bald eagles occur 

in Sonoran Desert and transitional 

communities there, as do those in 

Arizona and California. As discussed 

above, we have excluded from the 

expanded potential DPS bald eagles 

occurring in Baja California, Mexico. 

There are additional bald eagle 

breeding areas within Arizona but 

outside of the expanded potential DPS 

boundary. These breeding areas include 

Canyon de Chelly, Luna, Becker, 

Crescent, Greer, Woods Canyon, and 

Lower Lake Mary. These breeding areas 

were excluded because they are not 

located within the Sonoran Desert. 

Banding and Monitoring Information 

Bird banding and resighting are 

important tools used to answer 

questions regarding the biology and 

movement of individual birds (U.S. 

Geological Survey 2008, p. 1). The 

techniques used on bald eagles in the 

Southwest are consistent with marking 

technique standards (Varland et al. 

2007, pp. 222–228). Within this 

analysis, we use banding and resighting 

data for bald eagles to determine if bald 

eagles in the Sonoran Desert Area are 

markedly separate from other breeding 

populations of bald eagles. Specifically, 

we use banding and resighting data to 

determine if bald eagles originating in 

areas outside the Sonoran Desert Area 

have moved into the Sonoran Desert 

Area to breed (immigration), or if bald 

eagles originating in the Sonoran Desert 

Area have moved out of the Sonoran 

Desert Area to breed (emigration). 

We used bald eagle banding and 

resighting information collected 

between 1987 and 2007 as this is the 

time period during which banding and 

resighting efforts were most thorough in 

the Southwest. Banding of bald eagle 

nestlings began prior to this time in 

Arizona, starting in approximately 1977, 

and multiple researchers contributed to 

early banding efforts (Hildebrandt and 

Ohmart 1978; Haywood and Ohmart 

1980, 1981, 1982, 1983; Grubb 1986), as 

summarized in Hunt et al. 1992 (pp. 

C181–C202). However, early banding 

efforts were opportunistic, and the 

bands used at that time were difficult to 

read without capturing birds or 

recovering dead birds. As a result, little 

resight information was gained. 

Beginning in 1987, biologists increased 

efforts to band all nestlings and 

improved the effectiveness of banding 

and resighting by using color visual 

identification bands, which are more 

easily identified (Hunt et al. 1992, pp. 

C181–C202; Driscoll et al. 2006, p. 26). 

In total, the banding and resighting 

effort for bald eagles in Arizona has 

continued for 30 years with the last 20 

years using the more informative color 

bands. 

To determine the movement of 

breeding bald eagles in our target time 

period of 1987 to 2007, we relied on 

data from two datasets. The first dataset, 

called the Bird Banding Lab (BBL) 

dataset, is derived from data collected 

and collated by the U.S. Geological 

Survey Bird Banding Laboratory (U.S. 

Geological Survey 2008). The BBL 

dataset consists of over 19,000 records 

for bald eagles throughout the species’ 

range, including those banded in the 

Southwest. The second dataset, called 

the AGFD dataset, is derived from data 

compiled and used by Allison et al. 

(2008) in a demographic analysis for 

bald eagles in Arizona. 

Because our analysis focused on 

determining whether or not there is 

immigration or emigration of bald eagles 

to and from the Sonoran Desert Area, we 

analyzed bald eagles banded as 

nestlings and resighted as adults. Using 

only those birds banded as nestlings 

ensures that the origin of the banded 

birds is known, and that young birds 

originating in other areas are not 

included in the analysis. Using only 

resight information for breeding bald 

eagles eliminates data associated with 

juvenile migrants, which would not be 

contributing to the breeding population. 

Generally, age five is accepted as the age 

at which adult bald eagles breed 

throughout most of the species’ range. 

For this reason, when evaluating the 

nationwide BBL dataset, we considered 

bald eagles 5 years of age or older as 

breeding adults. However, for the AGFD 

dataset, where there are numerous 

instances of bald eagles breeding at 4 

years of age in Arizona (Allison et al. 

2008), we considered bald eagles 4 years 

of age or older as breeding adults. 

Immigration Into the Sonoran Desert 

Area 

For purposes of this analysis, 

immigration is defined as the movement 

of individuals banded as nestlings 

outside of the Sonoran Desert Area that 

are subsequently resighted as breeding 

birds inside the Sonoran Desert Area. In 

our analysis of the likelihood of bald 

eagle immigration into the Sonoran 

Desert Area from areas in closest 

proximity to the Sonoran Desert Area, 

we used data from the AGFD and the 

broader BBL dataset and considered 

bald eagle banding and resighting 

information from the States in proximity 

to the Sonoran Desert Area, including 

California, Colorado, Nevada, New 

Mexico, Texas, and Utah, as well as 

birds in Arizona but outside of the 

Sonoran Desert Area (see Table 1). 

TABLE 1—RECORDS FOR BALD EAGLES BANDED AS NESTLINGS IN AREAS OUTSIDE THE SONORAN DESERT AREA AND

RESIGHTED AS BREEDING BIRDS FROM 1987 TO 2007 (U.S. GEOLOGICAL SURVEY 2008; K. MCCARTY, AGFD, 

PERS. COMM. 2009; DRISCOLL et al. 2006, P. 49) 

[Please note that the table summarizes data from 1987 to 2007. Available data from 2008 are not as thorough, but they are consistent with the 

findings from the data reported. Further, the Texas bird resighted in Arizona occurs at a high-elevation nest outside of the Sonoran Desert 

area. Note we know of no banding information for birds banded in Mexico outside the Sonoran Desert area] 

State where banded 

Number of 

nestlings banded 

in areas in close 

proximity to the 

Sonoran Desert 

area between 

1987 and 2002 

Number of 

banded nestlings 

resighted as 

breeding birds 

between 1987 

and 2007 

States where banded eagles were resighted 

Number of 

resightings in the 

Sonoran Desert 

area 

Arizona outside the Sonoran Desert Area 12 0 ................................................................... 0 

California ................................................... 103 13 (12.6%) British Columbia, CA, WA ........................ 0 

Colorado ................................................... 152 7 (4.6%) CO, WY .................................................... 0 

Nevada ...................................................... 0 0 (0%) ................................................................... 0 


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TABLE 1—RECORDS FOR BALD EAGLES BANDED AS NESTLINGS IN AREAS OUTSIDE THE SONORAN DESERT AREA AND

RESIGHTED AS BREEDING BIRDS FROM 1987 TO 2007 (U.S. GEOLOGICAL SURVEY 2008; K. MCCARTY, AGFD, 

PERS. COMM. 2009; DRISCOLL et al. 2006, P. 49)—Continued 

[Please note that the table summarizes data from 1987 to 2007. Available data from 2008 are not as thorough, but they are consistent with the 

findings from the data reported. Further, the Texas bird resighted in Arizona occurs at a high-elevation nest outside of the Sonoran Desert 

area. Note we know of no banding information for birds banded in Mexico outside the Sonoran Desert area] 

State where banded 

Number of 

nestlings banded 

in areas in close 

proximity to the 

Sonoran Desert 

area between 

1987 and 2002 

Number of 

banded nestlings 

resighted as 

breeding birds 

between 1987 

and 2007 

States where banded eagles were resighted 

Number of 

resightings in the 

Sonoran Desert 

area 

New Mexico .............................................. 0 0 (0%) ................................................................... 0 

Texas ........................................................ 64 5 (7.8%) AZ, CA, NE, NM, TX ................................ 0 

Utah .......................................................... 6 0 (0%) UT ............................................................. 0 

Total ................................................... 337 25 (7.4%) ................................................................... 0 

Using the AGFD dataset, Allison et al. 

(2008, p. 25) indicate that anticipated 

survival rates for fledglings to age four 

is 28 percent. It should be noted that the 

mortality rates derived by Allison et al. 

(2008, p. 4) are based on modeling; 

however, the model was based on data 

collected over a 10-year period from 

1993 to 2003. 

The information summarized in Table 

1 indicates that 337 bald eagles were 

banded as nestlings between 1987 and 

2002 (the latest year for which a banded 

cohort could reach 5 years of age by 

2007) in the areas outside of but in 

proximity to the Sonoran Desert Area. 

Applying the survival rate of 28 percent 

to the 337 bald eagles reported banded 

as nestlings in Table 1, we would 

anticipate that approximately 94 

nestlings would have survived to age 

four. Only 25 of the banded nestlings 

were resighted as adults, and the fate of 

the remaining 69 nestlings is unknown. 

However, none of the 25 banded 

nestlings were resighted as breeding 

birds within the Sonoran Desert Area 

(see Table 1). 

While the number of banded and 

resighted birds in Table 1 is small, given 

the intensive effort in Arizona to 

identify the origins of banded breeding 

birds, we believe some inference is 

possible suggesting that the probability 

of nestlings originating outside of the 

Sonoran Desert Area and immigrating 

into the Sonoran Desert Area to breed is 

low. 

There is no known immigration from 

the Canyon de Chelly, Lower Lake 

Mary, Becker, Woods Canyon, Crescent, 

Greer, and Luna Lake breeding areas 

located at higher elevations within 

Arizona outside of the Sonoran Desert 

Area. To date, 29 nestlings produced at 

these breeding areas have been banded. 

Twenty-five of these were banded at the 

Luna breeding area from 1994–2000, 

2002–2005, and in 2007, with 22 of 

them fledging successfully (K. McCarty, 

AGFD, pers. comm. 2009). As of 2008, 

none of these banded offspring are 

known to have entered the breeding 

population of bald eagles in the Sonoran 

Desert Area (AGFD 2008a, pp. 1–2). The 

male bird at the Crescent breeding area 

is from the Luna breeding area (the 

female is unbanded) (Jacobson et al. 

2004, p. 16). Similarly, the male bird at 

the Greer breeding area is from the Luna 

breeding area, and the female is 

unbanded (McCarty and Jacobson 2008, 

p. 9). Lower Lake Mary fledged four 

young in 2005 and 2006, and the young 

were banded. The Woods Canyon and 

Greer breeding areas were first detected 

in 2008, and no young fledged that year 

from either breeding area. Six young 

have successfully fledged from Canyon 

de Chelly as of this date, none of which 

were banded (AGFD 2006, pp. 1–2; 

AGFD 2007, pp. 1–2; Jacobson et al. 

2007, pp. 16–19; AGFD 2008a, pp. 48– 

49; AGFD 2008, unpubl. data; AGFD 

2009, pp. 1–2). 

Biologists, primarily R. Mesta, 

estimate that, due to difficulty in 

accessing territories in Sonora, Mexico, 

they are able to monitor approximately 

40 to 60 percent of the known nest sites 

each year, and 20 to 30 percent of the 

known birds are observed while visiting 

these territories. Approximately 80 

percent of the birds detected have been 

examined for auxiliary markers, such as 

colored bands, and biologists believe 

that if marked bald eagles were 

occupying known territories after 1990, 

they would likely have been detected. 

However, they note that, in years in 

which surveys are conducted, breeding 

areas are visited only once and for a 

short period of time, which would make 

it easy to miss an individual eagle. They 

note that, in 1992, an adult at the Fig 

Tree breeding area had a yellow wing 

tag (potentially indicating it had 

originated in Texas or Florida) that 

could not be read, but no one has 

observed the bird since ((Driscoll and 

Mesta 2005, in prep., p. 62; R. Mesta, 

Service, pers. comm. 2008, Ortego et al. 

2009, p. 10). 

Emigration From the Sonoran Desert 

Area 

Emigration is defined here as the 

movement of individuals originating in 

the Sonoran Desert Area to areas outside 

the Sonoran Desert Area where they are 

resighted as birds of breeding age. Our 

analysis of data from the BBL dataset 

found that 41 of the 42 nestlings (97.6 

percent) banded within the Arizona 

portion of the Sonoran Desert Area were 

subsequently resighted within the 

Sonoran Desert Area. Only one eagle 

(2.4 percent) of breeding age was 

resighted outside of the Sonoran Desert 

Area, near Temecula, California (see 

Table 2). The BBL dataset shows that 

there were 371 bald eagles banded in 

Arizona between 1987 and 2007. With 

anticipated survival rates from fledgling 

to 4 years of age at 28 percent, we 

estimate that approximately 104 

nestlings should have survived to age 

four. While we know that 42 were 

resighted, the fate of the remaining 62 

birds is unknown. 


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TABLE 2—BALD EAGLES BANDED IN ARIZONA BETWEEN 1987 AND 2002 AND RECAPTURED OR RESIGHTED AS BIRDS OF

BREEDING AGE

[U.S. Geological Survey 2008)] 

State Number of birds 

(% recovered) Notes 

Within the Sonoran Desert Area 

Arizona .......................... 40 (95.2%) 

Sonora, Mexico ............. 1 (2.4%) Records indicate this bird was an adult entangled in fishing line at El Novillo Reservoir in Sonora. There was no breeding area at the reservoir, and the bird was not subsequently detected at a breeding area. 

Subtotal .................. 41 (97.6%) 

Outside of the Sonoran Desert Area 

California ....................... 1 (2.4%) This bird established a breeding area in California near Temecula. Birds in this breeding area 

were not successful in reproducing, and the nest site subsequently burned down (AGFD 

2008a, p. 6). 

Colorado ........................ 0 (0%) 

Nevada .......................... 0 (0%) 

New Mexico ................... 0 (0%) 

Oklahoma ...................... 0 (0%) 

Texas ............................. 0 (0%) 

Utah ............................... 0 (0%) 

Subtotal .................. 1 (2.4%) 

Total ................ 42 (100%) 

With respect to emigration, data in the 

AGFD dataset, a separate dataset than 

the BBL discussed above, illustrate the 

fate of 89 of 314 nestlings banded 

within the Sonoran Desert Area. Only 1 

of the 89 birds was documented 

breeding outside the Sonoran Desert 

Area. Fifty returned to breed in the 

Sonoran Desert Area, 1 bred 

(unsuccessfully) in California, and 38 

were known to have died before 

breeding (see Table 3) (Allison et al. 

2008, p. 19). Allison et al. (2008, p. 7) 

note that, from 1987 through 2003, 83 

percent of known fledglings in the 

Sonoran Desert Area were banded. 

Traditional ecological knowledge about 

bald eagles supports these data on 

emigration. Western Apache informants 

having expert knowledge of bald eagles 

in the Sonoran Desert Area testified that 

adult eagles do not leave Arizona. 

TABLE 3—DISPOSITION OF ARIZONA

BALD EAGLES BANDED AS

NESTLINGS FROM 1987 TO 2003 

[Allison et al. 2008, p. 19] 

Fate of nestlings Number of 

eagles 

Dead before fledging ................ 123 

Unbanded Nestlings ................. 62 

Banded Nestlings—Fate Unknown .................................... 225 

Banded Nestlings—Fate Known 

Dead before Breeding ........... 38 

Bred in Arizona ..................... 50 

TABLE 3—DISPOSITION OF ARIZONA

BALD EAGLES BANDED AS

NESTLINGS FROM 1987 TO 2003— 

Continued 

[Allison et al. 2008, p. 19] 

Fate of nestlings Number of 

eagles 

Bred in California .................. 1 

Total ................................... 499 

Banding and resighting efforts have 

not been as intensive in the areas in 

close proximity to the Sonoran Desert 

Area as they have been in Arizona, 

including the Sonoran Desert Area. We 

sent a questionnaire to bald eagle 

biologists in surrounding States in 2008 

in an attempt to determine the level of 

banding and monitoring efforts in some 

of these regions. In response to the 

questionnaire, we determined that 

surveys for breeding birds occur 

annually at Santa Cruz and Santa Rosa 

Islands off the coast of California, as 

well as in southern California at Lake 

Hemet. In survey efforts for these areas, 

all known territories and 100 percent of 

the known birds are visited, and no 

birds have bands or markers from 

Arizona (Hoggan 2008, pp. 1–2; P. 

Sharpe, pers. comm. 2008). 

Additionally, less-formal monitoring 

occurs in other areas in California 

through a variety of agencies and 

interested groups, including the U.S. 

Forest Service, the California 

Department of Fish and Game, the 

Ventana Wildlife Society, and the 

Channel Islands Live! Web site with 

similar results (i.e., no birds with bands 

from Arizona have been reported). In 

addition, sites known to support 

breeding pairs, such as the Copper Basin 

site, are monitored regularly. 

Six New Mexico territories have been 

monitored closely since their discovery 

in 1979, with no bands or markers from 

Arizona observed (S. Williams, pers. 

comm. 2008). Beginning in 1974, the 

Colorado Division of Wildlife began 

monitoring nesting activity, and 

currently monitors approximately 40 of 

their 80 nests each year, and bands 

eaglets at approximately one-third of 

those (Colorado Division of Wildlife 

2008, p. 1). No bands or markers from 

Arizona were observed. 

We have received no data for Utah or 

Nevada. Information on bald eagles 

banded within Arizona but outside the 

Sonoran Desert Area is summarized 

above under the ‘‘Immigration into the 

Sonoran Desert Area’’ discussion above. 

The data from areas in close 

proximity to the Sonoran Desert Area 

are not as thorough as those collected in 

Arizona, including in the Sonoran 

Desert Area. However, the banding and 

monitoring effort for breeding bald 

eagles in Arizona over a 30-year period 

has revealed only one breeding bird to 

date that immigrated into Arizona (Luna 

Lake, outside the Sonoran Desert Area). 


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We anticipate that, if immigration is 

occurring at such a low level, the same 

could be true of emigration as there are 

no known barriers that would favor 

emigration over immigration. 

Conclusion on Banding Data 

We find that the data on banding and 

resighting, while not extensive for areas 

in proximity to the Sonoran Desert Area, 

are collectively sufficient to document 

that bald eagles in the Sonoran Desert 

Area experience limited or rare 

reproductive interchange with bald 

eagles outside the Sonoran Desert Area. 

Bald eagle banding and resighting 

studies have been ongoing for greater 

than 30 years in Arizona, with the last 

20 years using the more informative 

color bands. As reported in the BBL 

dataset, of the 79 nestlings banded in 

Arizona and later resighted, 1 emigrated 

to California, outside of the Sonoran 

Desert Area, and never successfully 

reproduced. This finding indicates that 

97.6 percent of the bald eagles banded 

and resighted as breeding birds 

originated and returned to breed in the 

Sonoran Desert Area, with only 2.4 

percent (one bird) of breeding birds 

resighted in other areas (Table 2). 

Similarly, the AGFD dataset indicates 

that, for the nestlings banded between 

1987 and 2003 in areas outside of but 

in close proximity to the Sonoran Desert 

Area and resighted as breeding birds, 

none have immigrated to breed in the 

Sonoran Desert Area. 

While it is not possible to band and 

resight all bald eagles as breeding birds, 

the information provided suggests that 

the majority of breeding bald eagles 

within the Sonoran Desert Area 

population originated in the Sonoran 

Desert Area population, and have not 

been known to emigrate elsewhere to 

become part of a breeding population. 

There is one documented case of 

emigration for a bald eagle that 

originated in Arizona and established a 

breeding area outside of the Sonoran 

Desert Area in Temecula, California. No 

successful reproduction occurred, and 

that nest subsequently burned down 

(AGFD 2008a, p. 6). 

Data have been collected over a 

substantial time period under this effort, 

during which only one instance of a 

possible immigration and only one 

instance of emigration have been 

observed within the Sonoran Desert 

Area. We believe it is reasonable to 

conclude that in rare instances, 

immigration or emigration of an 

occasional bald eagle may occur; 

however, we consider the results from 

this 20-year period sufficient to 

document a marked separation of 

breeding populations. Our DPS Policy 

does not require complete isolation, and 

allows for some limited interchange 

among population segments considered 

to be discrete (61 FR 4722; February 7, 

1996). Based on the results of these 

banding and resighting data in Arizona 

and in neighboring States, we conclude 

that the Sonoran Desert Area bald eagles 

are not interbreeding with other 

populations, although some intermixing 

may occur at a very small rate. We 

conclude that the best scientific data 

available indicates a marked separation 

of Sonoran Desert Area bald eagles from 

bald eagles outside of the Sonoran 

Desert Area. 

Natal Dispersal and Fidelity 

Bald eagles are known to return close 

to their place of birth to breed 

(Stahlmaster 1987, p. 41). To illustrate 

the potential for breeding bird exchange 

between populations, the Service 

examined the records of bald eagles that 

were banded as nestlings and recovered 

5 or more years later at breeding age. We 

analyzed data associated with the eagles 

in the lower 48 States to derive a 

median dispersal distance of 43 mi (69 

km) from their natal site to their 

breeding area. Known nesting sites were 

then buffered by 43 mi (69 km) to 

determine the amount of breeding bird 

exchange that typically occurs (Service 

2008, pp. 17–18). Based on this analysis, 

Sonoran Desert Area bald eagles in the 

United States are separated from other 

southwestern populations by distances 

exceeding the median dispersal distance 

of 43 mi (69 km) for the species. The 

higher elevation breeding areas in 

Arizona are an exception to this 

separation, as they are less than 43 mi 

(69 km) from Sonoran Desert Area bald 

eagles; however, we believe these birds 

to be reproductively isolated from 

Sonoran Desert Area bald eagles, as 

described in the discussions on 

immigration above. 

Observations of actual dispersal 

behavior support the same conclusion 

as that derived from the modeling 

exercise discussed above. Hunt et al. 

(1992, p. A144) surveyed biologists 

studying nine bald eagle populations 

throughout North America consisting of 

more than 2,000 breeding pairs of bald 

eagles. Of those breeding pairs, only two 

adults were observed to breed outside of 

their natal area. Mabie et al. (1994, p. 

218) similarly concluded through their 

study in Texas and the Greater 

Yellowstone ecosystem that bald eagles 

tend to breed near their natal area. 

Gerrard et al. (1992, pp. 159, 164) 

observed four marked adults in 

Saskatchewan, Canada, and determined 

that they bred within 15.5 mi (25 km) 

of their natal territory. 

Natal dispersal patterns for Sonoran 

Desert Area bald eagles are similar to 

those in the studies discussed above. 

Data from 21 female and 35 male bald 

eagles in Arizona indicate that adult 

females dispersed an average of 68.1 mi 

(109.7 km) from their natal areas, while 

males dispersed an average of 28.0 mi 

(45.1 km) from their natal areas to breed 

(Allison et al. 2008, p. 30), but remained 

within the Sonoran Desert Area. 

Morphological Differences 

Emigration and immigration may also 

be influenced by the morphology of 

birds in different populations. Breeding 

bald eagles in the Sonoran Desert Area 

are smaller than those in northern 

States, which is typical of species in 

different latitudes (AGFD 2008a, p. 1). 

This is consistent with Bergmann’s 

Rule, which states that in the northern 

hemisphere, animals in warmer, 

southern environments are generally 

smaller than their counterparts in cooler 

northern climates (Futuyma 1986, pp. 

104–105). Stahlmaster (1987, pp. 16–17) 

found that northern eagles are larger and 

heavier than their southern 

counterparts. Hunt et al. (1992, pp. 

A158–A161) compared the means of 

nine standard morphological 

measurements (e.g., tail length, weight, 

beak depth) from adult eagles in 

Arizona to those from Alaska, northern 

California, and the Greater Yellowstone 

ecosystem. Measurements from adult 

Arizona eagles were smaller than mean 

measurements of other populations for 

all morphological characteristics except 

two: Depth of the bird’s leg bone and arc 

of its wing. Using a statistical analysis 

(t-Test), 26 different comparisons were 

made between the nine morphological 

characteristics. Test results indicated 

that male Arizona eagles were 

significantly smaller than males of the 

other three populations in 21 of those 26 

comparisons (Hunt et al. 1992, p. A160; 

Driscoll and Mesta 2005, in prep. p. 60). 

Adult females from Arizona were 

significantly smaller than females of the 

other populations in 14 of 26 

comparisons. Gerrard and Bortolotti 

(1988, p. 14) note that bald eagles in 

Florida that are farther south than 

Arizona are the smallest. Hunt et al. 

(1992, p. A165) indicate the size 

difference was significant enough that 

they believed a decision to release birds 

into Arizona from elsewhere should be 

considered only as a last resort, because 

the size difference could potentially be 

an adaptation to desert conditions 

which could be disrupted by the 

introduction of foreign genes. As 

discussed below, given that all bald 

eagles in southern latitudes are smaller 

than those at northern latitudes, the best 


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available information suggests that that 

the Sonoran Desert Area bald eagles do 

not provide any unique adaptations 

important to the conservation of the 

species as a whole. 

Another possible adaptation 

mentioned by bald eagle experts is the 

possible differences in egg shell 

characteristics of Arizona bald eagles 

from bald eagles in other parts of the 

range of the species. Hunt et al. (1992) 

discuss pores in eggshells of bald eagles 

in Arizona and some of the public 

comments (including some eagle 

experts) questioned whether or not 

these pores may have an effect on water 

loss from bald eagle eggs in the arid 

environment. Hunt et al. (1992) note 

that the pores are actually one to two 

orders of magnitude smaller than those 

in California bald eagle eggs; however, 

they did not reach any conclusions as to 

the significance that this may have to 

Arizona eagles. We also do not draw any 

conclusions from this information given 

the small sample size (four eggs). 

Morphological differences, whether 

due to local adaptations due to natural 

selection and a small amount of gene 

flow (Hunt et al. 1992, p. A163) or 

simply to Bergmann’s Rule, may reduce 

the success of immigration and 

emigration efforts. Bergmann’s Rule 

holds that the surface area to body 

weight ratio decreases as body weight 

increases, meaning that a large body 

loses proportionately less heat than a 

small one, which is advantageous in a 

cool climate, but disadvantageous in a 

warm one (Allaby 1991, p. 52). Thus if 

birds from further north immigrated into 

Arizona they could be at a competitive 

disadvantage coping with the hot 

climate during the breeding season. 

Similarly, if Arizona birds emigrated to 

far northern areas they would likely be 

at a competitive disadvantage for 

resources due to an inability to compete 

with birds in those areas, which are 

larger in size (AGFD 2008a, p. 5). In 

addition, Driscoll et al. 1999 (p. 223) 

note that if gene flow into Arizona from 

the north or west, where eagles are 

larger, had occurred, it should at least 

be reflected in the overall variance of 

measurable characteristics (i.e. standard 

morphological measurements for raptors 

such as tarsus width, length of feathers, 

arch of wing, etc.), and that they found 

no suggestion of that variance within 

the Arizona sample. 

For these reasons, it is unlikely that 

bald eagles interchange in a north-tosouth direction, or vice versa. The adult 

eagle that immigrated from Texas to 

establish a high-elevation nesting in 

Arizona, and the eagle that left Arizona 

to establish a breeding area (still within 

the Sonoran Desert Area) in extreme 

southeastern California near the 

Colorado River both dispersed laterally, 

with no north or south immigration or 

known emigration of breeding birds. 

Lack of Population Sources 

The immigration of adult bald eagles 

into the Sonoran Desert Area population 

from populations in relatively close 

proximity to the Sonoran Desert Area is 

likely limited by small population sizes 

in surrounding States, and their 

separation from the Sonoran Desert Area 

by long distances, over unoccupied 

habitats. There are currently eight 

known breeding areas in southern 

California in addition to populations on 

Santa Cruz and Santa Rosa Islands off 

the coast of California (California 

Department of Fish and Game 2008, pp. 

2–3; Ventana Wildlife Society 2008, 

p. 1). Colorado has a somewhat larger 

population, with approximately 80 

active breeding areas (Colorado Division 

of Wildlife 2008, p. 1). Nevada has 

approximately one inactive and five 

active breeding territories. Two 

territories, Carson River and Lahontan 

Reservoir, last had eagles detected in 

2002 and 2006, respectively. The 

occupancy of two others is not yet 

confirmed. The remaining breeding area 

produced only two young from 1996 to 

2007 (K. Kritz, Service, pers. comm. 

2008). Utah has approximately 10 active 

territories and one inactive breeding 

territory (N. Darnall, Service, pers. 

comm. 2008). For New Mexico, the 

population of bald eagles consists of 

four currently occupied territories (H. 

Walker, NMDGF, pers. comm. 2009). 

West Texas currently has one active 

breeding territory west of the 100th 

Meridian. This territory has been active 

since 1994 (C. Boal, pers. comm. 2009). 

Marked Separation as a Consequence of 

Ecological Factors 

A final factor isolating Sonoran Desert 

Area bald eagles is the unsuitability of 

habitat in areas surrounding the 

Sonoran Desert Area for occupancy by 

breeding birds. The majority of the bald 

eagle population in the Sonoran Desert 

Area occurs in central Arizona within 

the riparian areas of the Sonoran Desert 

as described in Brown (1994, pp. 180– 

221) and adjacent vegetation 

communities. Across the western 

United States, there are large geographic 

areas where breeding bald eagles are 

rarely found. These areas are associated 

with the Great Basin and Mohave 

Deserts, indicating that conditions in 

these desert biotic communities are not 

suitable for occupancy. In contrast, the 

Sonoran Desert and its subdivisions, 

where nesting bald eagles within the 

Sonoran Desert Area are located, are 

suitable for breeding areas because of 

the availability of water, prey, and trees 

suitable for nesting and perching. The 

Sonoran Desert scrub vegetation 

community is unique from other desert 

scrub formations in North America in its 

tropical and subtropical influences. 

Within the community, the riparian or 

riverine habitat occupied by breeding 

bald eagles is limited to areas where 

there is sufficient winter precipitation to 

support vegetation along streams 

(Brown 1994, p. 269). 

Western Apache traditional ecological 

knowledge corroborates these data 

regarding bald eagles within the 

Sonoran Desert Area being ecologically 

separated from other populations. Three 

Apache place names use the term Itsa 

Bigow (‘‘bald eagle’s home’’). Apaches 

use the term gowa (meaning ‘‘home’’) 

referring to the eagle’s entire habitat, as 

opposed to the term bit’oh (‘‘its nest’’). 

According to Basso (1996), the Western 

Apaches’ perception of the land works 

in specific ways to influence Apaches’ 

awareness of themselves. The process of 

‘‘place naming’’ documents where and 

how Apaches learned about the 

environment and how they incorporated 

these names into social and 

environmental ethics (Basso 1996). This 

concept is further exemplified by the 

Apache word ‘‘ni’’, this expression 

translates to mean both ‘‘mind’’ and 

‘‘land,’’ and thus, the two words cannot 

be separated (Chairman Ronnie Lupe, 

pers. comm., 2008). The Apache bald 

eagle place names evoke an entire area 

or ecosystem of which the bald eagle is 

an intrinsic part. The place names 

include entire mountainsides composed 

of chaparral, pinyon-juniper woodland, 

and ponderosa pine forests, always in 

proximity to water (i.e., riparian areas) 

(Lupe et al. pers. comm. 2008). 

Bald eagles, including those in the 

Sonoran Desert Area, typically nest 

within 1 mi (1.6 km) of water. Bald 

eagles require cliff ledges, rock 

pinnacles or large trees or snags in 

which to construct nests (Driscoll et al. 

2006, pp. 19–20). Those areas most 

immediately surrounding the Sonoran 

Desert Area, which contain no known 

breeding eagles or suitable habitat, fall 

within the Great Basin and Mohave 

Deserts. Areas in the Great Basin and 

Mohave Deserts surrounding the 

Sonoran Desert Area lack the 

appropriate bald eagle habitat 

parameters of water, fish, and nesting 

areas. Nonbreeding bald eagles from 

other populations migrate through these 

areas to reach the Sonoran Desert Area. 

Therefore, we believe these desert areas 

result in a discontinuity of distribution 

of breeding birds, rather than as a 

barrier to dispersal, and serve to further 


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isolate Sonoran Desert Area bald eagles 

from those in other populations. 

Bald eagles nesting at high elevation 

in Arizona in areas in proximity to the 

Sonoran Desert Area occupy Petran 

Montane Conifer Forest and Plains, and 

Great Basin Grassland above the 

Mogollon Rim (Brown and Lowe 1994, 

map). These eagles are not believed to 

have originated from within the 

Sonoran Desert Area, as described 

above. Similarly, bald eagles occupying 

these areas are not known to have 

occupied Sonoran Desert habitat within 

the Sonoran Desert Area. These highelevation areas appear to be unsuitable 

to Sonoran Desert Area bald eagles, as 

indicated by the lack of emigration to 

these areas by eagles originating in the 

Sonoran Desert Area. 

Conclusion on Discreteness 

Based on the available information in 

the petition, scientific literature, 

traditional ecological knowledge, and 

information in our files regarding bald 

eagles in the Sonoran Desert Area, we 

have determined that the Sonoran 

Desert Area population of bald eagles is 

markedly separate from other 

populations of the species due to a lack 

of immigration to and emigration from 

surrounding bald eagle populations, and 

the fact that the areas immediately 

surrounding the Sonoran Desert Area 

lack the appropriate bald eagle habitat 

parameters of water, fish, and nesting 

areas and contain no known breeding 

bald eagles. Therefore, we have 

determined that the Sonoran Desert 

Area population meets the requirements 

of our DPS Policy for discreteness. 

Banding studies and resighting efforts 

demonstrate that breeding bald eagles in 

the Sonoran Desert Area are largely 

geographically separate from those in 

surrounding areas. Limited source 

populations and unsuitable habitat in 

surrounding areas further separate bald 

eagles in the Sonoran Desert Area from 

those in other areas. Although not 

absolute, we believe this separation to 

be marked, and to meet the intent of the 

DPS Policy for discreteness. We made a 

similar argument and drew the same 

conclusion for similar reasons in our 

final delisting rule for the species in the 

lower 48 States (72 FR 37246, July 9, 

2007). 

Significance 

If we determine that a population 

segment is discrete under one or more 

of the discreteness conditions described 

in the DPS Policy, we then evaluate its 

biological and ecological significance 

based on ‘‘the available scientific 

evidence of the discrete population 

segment’s importance to the taxon to 

which it belongs’’ (61 FR 4725). We 

make this evaluation in light of 

congressional guidance that the 

Service’s authority to list DPSs be used 

‘‘sparingly’’ while encouraging the 

conservation of genetic diversity (61 FR 

4722; February 7, 1996). Since precise 

circumstances are likely to vary 

considerably from case to case, the DPS 

Policy does not describe all the classes 

of information that might be used in 

determining the biological and 

ecological importance of a discrete 

population. However, the DPS Policy 

describes four possible classes of 

information that provide evidence of a 

population segment’s biological and 

ecological importance to the taxon to 

which it belongs. As specified in the 

DPS Policy (61 FR 4722), consideration 

of the population segment’s significance 

may include, but is not limited to the 

following: (1) Persistence of the 

population segment in an ecological 

setting that is unusual or unique for the 

taxon; (2) evidence that loss of the 

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 of its 

historic range; and (4) evidence that the 

discrete population segment differs 

markedly from other populations of the 

species in its genetic characteristics. 

Evidence with respect to any one of 

the classes of information listed in the 

DPS Policy may allow the Service to 

conclude that a population segment is 

significant to the taxon to which it 

belongs. Furthermore, the Service may 

consider other information relevant to 

the question of significance, as 

appropriate. 

Persistence in a Unique Ecological 

Setting 

As stated in the DPS Policy, the 

Service believes that occurrence in an 

unusual ecological setting may be an 

indication that a population segment 

represents a significant resource 

warranting conservation under the Act 

(61 FR 4724). In considering whether 

the population occupies an ecological 

setting that is unusual or unique for the 

taxon, we evaluate whether the habitat 

includes unique features not used by the 

taxon elsewhere and whether the habitat 

shares many features common to the 

habitats of other populations. The bald 

eagle: (1) Is continent wide in its 

distribution (stretching from the 

Aleutian Islands to Baja California, 

Mexico, and from northeastern Canada 

to Florida), (2) breeds from sea level to 

mountains as high as 10,000 feet, (3) 

lives in some of the driest areas in the 

United States and in some of the 

wettest, and (4) is capable of nesting in 

trees, on cliff faces, on the ground, and 

even in caves. In other words, the 

species is able to occupy a broad range 

of vegetation communities and 

ecosystems throughout North America. 

Because the bald eagle occurs in so 

many diverse environments, it is 

difficult to determine what the ‘‘usual’’ 

ecological setting is for the species, and, 

therefore, difficult to conclude that the 

bird’s presence in any particular 

ecological setting is ‘‘unusual,’’ possibly 

indicating significance under our DPS 

policy. 

Bald eagles in the Sonoran Desert 

Area inhabit a desert ecosystem 

characterized by hot and dry summers. 

On its face, this seems to represent an 

ecological setting that is highly unusual 

or unique for the species. For instance, 

according to Hunt et al. (1992, p. A163) 

and Glinski (1998, p. 52) bald eagle 

nesting habitats in Arizona are among 

the most unusual nesting habitats 

occupied by the species, with many of 

the nests located in open desert under 

conditions of high heat and low 

humidity. As a highly adaptable species, 

however, bald eagles are flexible with 

respect to habitat selection. They 

inhabit many diverse environments. 

They inhabit hot climates elsewhere, 

such as in Florida. They even inhabit 

other desert ecosystems in Baja 

California Sur (Henney et al. 1978, 

1993). Bald eagle breeding in Baja is 

limited, but nest sites are known from 

both the Pacific Ocean and Gulf of 

California sides of the peninsula, in arid 

and semi-arid ecosystems of the 

Sonoran Desert (Henney et al. 1978, 

1993). Bald eagles in desert habitats, 

including the potential Sonoran Desert 

Area DPS, essentially use the same 

ecological niche as those in other parts 

of their range. Bald eagles in the 

Sonoran Desert Area feed primarily on 

fish, consistent with bald eagles in other 

parts of the range. With respect to 

nesting requirements, according to Grier 

and Guinn (2003, p. 44), habitat 

structure and proximity to a sufficient 

food source are usually the primary 

factors that determine suitability of an 

area for nesting. Throughout their range, 

bald eagles are known to nest primarily 

along seacoasts and lakeshores, as well 

as along banks of rivers and streams 

(Stahlmaster 1987, p. 120). Similar to 

the remainder of the population, bald 

eagle breeding areas (eagle nesting sites 

and the area where eagles forage) in the 

Sonoran Desert Area are located in close 

proximity to a variety of aquatic sites, 

including reservoirs, regulated river 


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systems, and free-flowing rivers and 

creeks. 

Although the Sonoran Desert differs 

in some ways from other habitats that 

the bald eagle inhabits, every area 

differs somewhat from other occupied 

areas. Under the DPS Policy, for a 

population segment to qualify as a DPS 

it must be significant to the species to 

which it belongs. The Policy further 

lists four issues that the Service may 

consider in making this determination. 

Those considerations include whether 

the population segment persists in a 

unique or unusual ecological setting. 

However, the question of ecological 

setting is not considered in the abstract, 

or itself determinative as to whether a 

population segment is significant. As 

with the other considerations under the 

significance prong of the DPS Policy, it 

must be considered in the context of the 

population segment’s importance to the 

taxon to which it belongs. Thus, to the 

extent that a population segment 

arguably persists in an unusual 

ecological setting, the Service must 

consider how persistence in this setting 

may in fact be important to the taxon. 

Failure to consider this context would 

lead to the conclusion that an 

unreasonable and potentially infinite 

number of population segments are 

significant. However, our DPS Policy 

states that the requirement that a DPS be 

significant is intended to carry out the 

expressed congressional intent that this 

authority be exercised sparingly as well 

as to concentrate conservation efforts 

undertaken under the Act on avoiding 

important losses of genetic diversity. We 

conclude that the best information 

available does not indicate that 

persistence in the ecosystem of the 

Sonoran Desert Area is important to the 

species as a whole. 

We considered whether cliff nesting is 

an adaptation to the conditions in the 

Sonoran Desert Area that indicates that 

the southwest is an unusual or unique 

ecological setting for bald eagles. While 

Stahlmaster (1987, p. 121) noted that 

cliff nesting is common in Arizona, he 

also noted that exceptions to tree nests 

occur in other areas. Gerrard and 

Bortolotti (1988, p. 41) note that bald 

eagles in other areas may nest on cliffs 

if suitable trees are not available. This 

is supported by Buehler (2000) who 

states that bald eagles use ground nests 

(a category in which he includes nests 

built on cliff sides) in treeless regions 

such as Alaska, north Canada, islands 

off the coast of California, and Arizona. 

Bald eagles are known to nest on cliffs 

on the Channel Islands off California 

(NOAA 2006). Bald eagles in Alaska 

also are known to nest on cliffs, sea 

stacks, hillsides, and rock promontories 

where there are no suitable nest trees 

(Sherrod et al. 1976, p. 153). It is likely 

that up to 10 percent of the bald eagles 

in Alaska nest on the ground (Schempf 

pers. comm. 2007). Ground nesting has 

been documented in northwestern 

Minnesota and Florida but is the 

exception rather than the rule (Hines 

and Lipke 1991, pp. 155–157; Shea et al. 

1979, pp. 3–5). Eagles also nest in a 

variety of unconventional situations, 

such as utility poles, abandoned heavy 

equipment, mangroves, cacti (in Baja), 

and root wads washed up on sandbars. 

Cliff nesting in Sonoran Desert Area 

bald eagles does not seem to be an 

indication of a behavioral adaptation 

unique to the Sonoran Desert. Bald 

eagles will use whatever high nest sites 

are available near aquatic areas they 

inhabit; in the Sonoran Desert Area 

these sites often happen to be cliffs. In 

fact, although bald eagles use cliffs, 

ledges, and pinnacles for nesting in the 

Sonoran Desert Area, they have also 

nested there in cottonwood, willow, 

sycamore, pinyon pine, and ponderosa 

pine trees. Many Sonoran Desert Area 

eagle pairs have built and used both tree 

and cliff nests within their territories. 

This behavior demonstrates the 

flexibility in nest site selection that bald 

eagles have throughout the eagles’ entire 

geographic range. 

Bald eagles in the Sonoran Desert 

Area are smaller in size than many other 

bald eagles. However, as previously 

discussed, examination by latitude 

reveals differences between birds in the 

northern regions and birds in the 

southern regions in general. For 

instance, Stahlmaster (1987, pp. 16–17) 

notes northern eagles are much larger 

and heavier than their southern 

counterparts. This is consistent with 

Bergmann’s Rule, which holds that 

animal size increases with increasing 

latitude due to changes in 

environmental temperature. Consistent 

with this rule, Hunt et al. (1992, pp. 

A158–A161) report that bald eagles in 

Arizona are smaller than those in 

Alaska, California, and the Greater 

Yellowstone Region. Gerrard and 

Bortolotti (1988, p. 14) note that bald 

eagles in Florida, which is farther south 

than Arizona, are the smallest, with a 

gradation of small to large from south to 

north. Although this information might 

be interpreted as suggesting that all 

southern birds are significant to the 

taxon as a whole (since southern birds 

are smaller), it does not suggest that 

small size of the Sonoran Desert Area 

bald eagle in particular is important to 

the taxon as a whole. This is especially 

true given that Florida has one of the 

largest breeding populations of bald 

eagles in the lower 48 States, and bald 

eagles in Florida are reported to be even 

smaller than those in the Sonoran Desert 

Area. This information suggests that 

there are many bald eagles outside the 

Sonoran Desert Area that are smaller 

than those within it, diminishing any 

potential importance of small size in the 

Sonoran Desert Area to the taxon as a 

whole. 

We considered the belief of Hunt et al. 

(1992, p. A165) that the smaller size of 

Arizona bald eagles was significant 

enough that the introduction of foreign 

genes into the population might disrupt 

coadapted gene complexes (a group of 

genetic traits which have high fitness 

when they occur together, but which 

without each other have low fitness) 

specific to the population. Given there 

are smaller birds elsewhere in the bald 

eagle’s range, it is unlikely small size 

would be considered an indicator of 

coadapted gene complexes specific to 

bald eagles within the Sonoran Desert 

Area. We conclude that the best 

available information does not suggest 

the Sonoran Desert Area bald eagle 

population possesses coadapted gene 

complexes specific to the population. 

Thus, we conclude that the best 

available information does not suggest 

the Sonoran Desert Area bald eagles are 

important to the taxon as a whole due 

to coadapted gene complexes. 

Bald eagles in the Sonoran Desert 

Area breed earlier than many other bald 

eagles, which could indicate adaptation 

to the Sonoran Desert Area setting. 

However, as with bald eagle size 

variation, examination by latitude 

reveals differences between bald eagles 

in northern and bald eagles in southern 

regions, in general. Timing of various 

breeding events in bald eagles is tied to 

latitude of the nesting area, with eagles 

at more northern latitudes breeding at 

later dates (Stalmaster 1987, p. 63). 

Citing unpublished data, Watts et al. 

(2007) even note differences in breeding 

chronology with slight variation of 

latitude within the Chesapeake Bay 

region; pairs on the James River lay eggs 

four to six days earlier than pairs on the 

Potomac River. The breeding 

chronology of Florida birds is even 

earlier than those in the Sonoran Desert 

Area. Gerrard and Bortolotti (1988, p. 

76) note that bald eagles in Florida lay 

eggs from early November to midDecember. Henry et al. (1993 p.208) 

report that Baja California bald eagles 

are already incubating by mid January, 

which indicates a mid-December to 

early-January egg laying period. In 

Louisiana, bald eagles lay eggs between 

October and mid-March, but most 

clutches are complete by late December 

(Service 1989). Even bald eagles within 

the Chesapeake Bay region of Virginia 


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and Maryland, which experience a more 

mild (i.e. coastal) climate than their 

inland counterparts at similar latitude, 

are similar in their breeding chronology 

to those of the Sonoran Desert Area; 

bald eagles in the Chesapeake Bay 

region typically lay eggs between midJanuary and late February. Further 

evidence of variation in breeding 

chronology in bald eagles is given by 

Buehler (2000): 

Timing of laying varies with latitude. Bent 

(1937) reported range of egg dates (dates eggs 

were collected from nests) but because 

incubation is long (35 d), and eggs persist in 

abandoned nests, these data do not 

accurately document laying and incubation 

phenology. In Florida, breeding season is 

prolonged, with incubation beginning as 

early as Oct and as late as Apr; Apr breeding 

may be second attempt; most incubation 

initiated Dec–Jan (Broley 1947). On 

Chesapeake Bay, begin incubation last week 

in Jan to end of Feb (DAB). In Saskatchewan, 

laying is fairly synchronous, with 90% of 

pairs laying within a 10-d period in mid-Apr 

(Gerrard and Bortolotti 1988). In greater 

Yellowstone ecosystem, WY, clutch laid from 

early Mar–mid-Apr; later dates at greater 

elevations (Swenson et al. 1986). Eggs 

typically laid in Arizona late Jan–mid-Feb 

(Grubb 1983). Nests observed in Mexico had 

incubating adults in Jan; therefore, laying 

may have occurred from late Dec to early Jan 

(Henny et al. 1993). In Alaska and Yukon 

Territory, laying extends from late Apr to end 

of May, peaking in second week of May 

(Hensel and Troyer 1964, Blood and 

Anweiler 1990). 

Given that early breeding by bald 

eagles in the Sonoran Desert Area is not 

unique among eagles, and in fact occurs 

in some of the largest breeding areas in 

the lower 48 States, it is unlikely that 

early breeding by bald eagles in the 

Sonoran Desert Area is important to the 

species as a whole. 

Although the best available 

information indicates that the Sonoran 

Desert Area is in some ways a unique 

ecological setting, we know of no 

information suggesting bald eagle 

persistence in the Sonoran Desert Area 

is important to the species as a whole. 

In fact, the best information available 

indicates otherwise. Bald eagles are 

behaviorally flexible—they can and do 

persist in a broad range of ecological 

settings, and are known to nest on a 

variety of substrates when suitable trees 

are not available. As with many other 

vertebrates, bald eagles follow 

Bergmann’s rule; their size decreases 

with decreasing latitude. In addition, 

Sonoran Desert Area bald eagle breeding 

chronology is consistent with bald 

eagles in general; bald eagle breeding 

chronology occurs earlier with 

decreasing latitude and increasing 

temperature. Rather than possessing 

characteristics unique to the Sonoran 

Desert Area ecological setting that may 

be important to the species as a whole, 

bald eagles in the Sonoran Desert Area 

display the behavioral variability and 

follow the morphological and annual 

cycle (such as breeding chronology) 

trends of bald eagles throughout North 

America. In other words, the variability 

in bald eagle nest-site selection, timing 

of breeding, and size differences are 

noted elsewhere in the range where the 

species confronts similar limitations, 

such as the absence of nesting trees or 

high temperatures. Even though bald 

eagles persist in the Southwest desert 

setting, they remain consistently 

associated with aquatic sites, including 

reservoirs, regulated river systems, and 

free-flowing rivers and creeks. Bald 

eagles use whatever high nest sites are 

available near aquatic areas they inhabit 

in the Sonoran Desert Area; these sites 

often happen to be cliffs. These aquatic 

areas are common to eagle habitats 

throughout the species’ range, and the 

best available data indicate that the 

nesting preferences of the Sonoran 

Desert Area eagles are not unique to the 

taxon as a whole. 

We also considered whether the 

juvenile migration characteristics of 

Arizona bald eagles may suggest genetic 

adaptation. Hunt et al. (2009, p. 125) 

indicates that juvenile bald eagles from 

Arizona exhibit similar migrating 

characteristics, and that the similarity of 

these characteristics, which were 

exhibited while migrating solitarily, is 

evidence of genetic control of migration. 

Bald eagles as a species exhibit a 

‘‘complex pattern of migration 

dependent on age of the individual 

(immature or adult), location of 

breeding site (north vs. south, interior 

vs. coastal), severity of climate at 

breeding site (especially during winter 

but also possibly during summer), and 

year-round food availability (Buehler 

2000).’’ For example, bald eagles in 

northeastern North America migrate 

south in the fall and return north in the 

spring, whereas bald eagles in Florida 

move north in late spring and early 

summer and return south in the fall 

(Kerlinger 1989, p. 12). Kerlinger (1989, 

p. 57) discusses that natural selection 

has likely shaped the migratory strategy 

of birds. Natural selection likely exerts 

pressure over time to emphasize the 

survival of successful migration 

strategies, and therefore, successful 

genes. In other words, birds that make 

errors in migration are eliminated from 

the population and do not go on to 

reproduce and pass their genes to the 

next generation. Thus, the birds that do 

survive migration and reproduce 

successfully may become more 

genetically similar. Thus, the migration 

characteristics of bald eagles in the 

Sonoran Desert Area could be 

interpreted as providing anecdotal 

evidence that there may be some genetic 

adaptation in this population with 

respect to juvenile migratory behaviors; 

however, we know of no information 

suggesting that these potential 

adaptations are significant to the species 

as a whole, especially in light of the fact 

that a wide variety of migration 

strategies are utilized throughout the 

range of the species. 

Some members of the public 

questioned the future of the bald eagle 

given the possibilities associated with 

climate change. All but one model 

evaluating changing climatic patterns 

for the southwestern United States and 

northern Mexico predict a drying trend 

for the region (Seagar et al. 2007, pp. 

1181–1184). We acknowledge that 

drought and the loss of surface water in 

riparian and aquatic communities are 

related to changing climatic conditions 

(Seagar et al. 2007, pp. 1181—1184). 

The extent to which changing climate 

patterns will affect bald eagles in the 

Sonoran Desert Area is not known. 

However, because bald eagles are highly 

adaptable, the best available information 

indicates it is unlikely the Sonoran 

Desert Area population adds resiliency 

to the taxon as a whole. For this reason, 

it is also unlikely that the Sonoran 

Desert Area bald eagles will be 

significant to the species as a whole if 

the southwest becomes more arid in the 

future as predicted. 

Many biological opinions prepared by 

the Service in connection with section 

7 consultations in the Sonoran Desert 

and other Service documents issued 

over the last 30 years stated that Arizona 

bald eagles live in a unique ecological 

setting and demonstrate unique 

behavioral characteristics, including the 

use of cliffs instead of trees as nest sites, 

breeding at earlier times of the year, and 

development of smaller body sizes. 

Several comment letters, including 

those from bald eagle experts, referred 

to the Service’s previous management 

practice of recognizing the bald eagles 

in a Southwest Recovery Region 

separate unit. As stated above and in the 

final delisting rule (72 FR 37355), that 

was prior to the DPS policy of 1996, and 

we conclude that the DPS evaluation of 

significance should be evaluated per the 

policy, as described in this document. 

Some of these documents also stated 

that the Arizona bald eagles had been 

considered a distinct population for the 

purposes of section 7 consultation and 

recovery efforts under the Act. Many of 

these biological opinions and other 

documents were issued prior to the 


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Stahlmaster (1987) and Gerrard and 

Bortolotti (1988) publications, the 

issuance of the DPS Policy in 1996, or 

were abstracted from such earlier 

biological opinions without a reanalysis 

of their relevance. The term ‘‘unique 

ecological setting’’ was not used in these 

documents in the context of its meaning 

within the DPS Policy, which requires 

that the unique or unusual ecological 

setting be important to the conservation 

of the taxon as a whole. As discussed 

above, while the climate conditions 

differ in the Southwest compared to 

other parts of the range of the taxon 

where bald eagles are found, this 

attribute alone is not dispositive as to 

whether a population segment is 

significant under the DPS Policy. A 

unique or unusual ecological setting 

must also provide some element that 

makes the members of the population 

important to the taxon as a whole (61 FR 

4724–4725). 

In summary, Stahlmaster’s (1987, p. 

121) and Gerrard and Bortolotti’s (1988, 

p. 41) studies indicate that bald eagles 

in other parts of their range are known 

to nest on cliffs if suitable trees are not 

available. Hunt et al. (1992) note that 

Florida bald eagles are the smallest bald 

eagles, and that eagle size increases as 

the nest sites are located farther north. 

Stalmaster (1987) notes that bald eagles 

in Florida initiate breeding activities in 

October, even earlier than Sonoran 

Desert Area bald eagles. The best 

available scientific information 

indicates that the Sonoran Desert Area 

bald eagles are not unusual in these 

behavioral aspects. Instead, bald eagle 

behavior and morphology gradually 

changes at different latitudes from north 

to south. In fact, even though bald 

eagles do persist in the Southwest desert 

setting, they remain consistently 

associated with aquatic ecosystems as 

they do elsewhere. Bald eagles use 

whatever high nest sites are available 

near riparian areas they inhabit in the 

Sonoran Desert Area; these sites often 

happen to be cliffs. These riparian areas 

are common to eagle habitats 

throughout the species’ range. The 

question under the DPS Policy is 

whether persistence of a species in an 

unusual or unique ecological setting 

supports a conclusion that the discrete 

population segment is significant to the 

taxon to which it belongs. See National 

Association of Home Builders v. Norton, 

340 F.3d 835, 849 (9th Cir. 2003) 

(emphasizing that under the DPS Policy 

significance must be considered in 

relation to the taxon as a whole). The 

mere fact that a species persists in an 

ecological setting that differs to some 

degree from other ecological settings in 

which it is found does not mandate a 

finding that a population is significant 

to the taxon to which it belongs. Here, 

we find that the species’ persistence in 

the Sonoran Desert Area is not 

significant to the taxon as a whole 

because these particular eagles exhibit 

similar behavior and nesting 

adaptations to their setting as do bald 

eagles in other settings. 

Therefore, we conclude that the 

discrete population of bald eagles in the 

Sonoran Desert Area is not ‘‘significant’’ 

within the meaning of the DPS Policy as 

a result of persistence in a unique or 

unusual ecological setting. 

Significant Gap in the Taxon’s Range 

As stated in the DPS Policy, the 

Service believes that evidence that loss 

of the discrete population segment 

would result in a significant gap in the 

range of a taxon, is potentially an 

indication that a population segment 

represents a significant resource 

warranting conservation under the Act 

(61 FR 4724). As the Ninth Circuit has 

stated, ‘‘[t]he plain language of the 

second significance factor does not limit 

how a gap could be important,’’ 

National Ass’n of Home Builders v. 

Norton, 340 F.3d 835, 846 (9th Cir. 

2003). Thus, we considered a variety of 

ways in which the loss of the Sonoran 

Desert Area population might result in 

a significant gap in the range of the bald 

eagle in the lower 48 States (although 

this range is itself only a portion of the 

broader taxon. There has been much 

speculation about the loss of eagles in 

the Sonoran Desert Area given that 

repopulation of this area would have to 

occur from northern Mexico or adjacent 

States in the United States and available 

evidence indicates that little 

immigration has occurred in this 

population. We agree that the low 

number of eagles in neighboring States 

of the United States would likely 

require a large amount of time to 

repopulate the Sonoran Desert Area, if 

they ever did. The small number of bald 

eagles and large distances between 

neighboring populations currently limit 

immigration and emigration between 

them, and bald eagles in the neighboring 

populations would have to increase 

their population size and expand their 

distribution to occupy the gaps. 

Given that repopulation of the 

Sonoran Desert Area, if extirpated, 

through immigration is unlikely in the 

foreseeable future due to unsuitable 

habitat and limited population sources, 

we must evaluate whether loss of this 

population would create a significant 

gap in the range of the taxon. Bald 

eagles in the Sonoran Desert Area are 

neither numerous nor constitute a 

significant percentage of the bald eagles 

throughout the range of the taxon. In 

2009, 48 pairs were documented in the 

Arizona portion of the Sonoran Desert 

Area (McCarty and Jacobson 2009, p. 8), 

which is where most of the birds in the 

Sonoran Desert Area population occur. 

This represents less than one half of 1 

percent of the current estimated number 

of breeding pairs of bald eagles in the 

lower 48 States. Because the taxon as a 

whole also includes bald eagles in 

Canada and Alaska, the number of 

breeding pairs in the Sonoran Desert 

Area represents much less than one half 

of a percent of the number of breeding 

pairs throughout the range of the 

species. In addition, the Arizona portion 

of the Sonoran Desert Area did not 

support a large proportion of the bald 

eagle population historically. A small 

number, estimated at 15–20 breeding 

pairs, historically bred in this area (Tilt 

1976, p. 15). Only one pair was 

documented in the Mexico portion of 

the Sonoran Desert Area population, but 

surveys were very limited. 

Given the historical and current 

population number of bald eagles 

throughout the range of the taxon, the 

Sonoran Desert Area population of bald 

eagles represents a relatively small 

number of breeding pairs in 

comparison. On balance, having 

reviewed all the relevant information, 

we conclude that loss of eagles in the 

Sonoran Desert Area would not 

represent a significant gap in the range 

of the species due to a loss of 

biologically distinctive traits or 

adaptations, or genetic variability of the 

taxon. The actual amount of suitable 

bald eagle habitat in the Sonoran Desert 

Area is in general limited and represents 

a minute fraction of the total suitable 

habitat available for bald eagles 

throughout their range. The limited size 

of the current and historical bald eagle 

population in the Sonoran Desert Area 

directly reflects that fact. Thus, we 

conclude that loss of the Sonoran Desert 

Area would not result in a significant 

gap in the range of the taxon. 

As discussed previously in this 

document, we divided the lower 48 

States into five recovery regions to 

facilitate the recovery of the bald eagle. 

In the southwestern United States bald 

eagles were managed under the 

Southwest Bald Eagle Recovery Region, 

which encompassed Oklahoma, Texas 

west of the 100th meridian, all of New 

Mexico and Arizona, and those portions 

of southeastern California that border 

the lower Colorado River. Several 

comment letters, including those from 

bald eagle experts, referred to our 

previous management practice of 

recognizing the bald eagles in a 


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Southwest Recovery Region separate 

unit. As has been stated here and in the 

final delisting rule (72 FR 37355), we 

delineated bald eagle Recovery Regions 

prior to the DPS Policy of 1996. Thus, 

the boundaries of these units were not 

delineated based on the significance 

criteria of our DPS policy. These 

boundaries, therefore, may have little 

baring on an analysis of whether the 

loss of the Sonoran Desert Area 

population would result in a significant 

gap in the range of bald eagles in North 

America. We conclude that the DPS 

evaluation of significance should be 

evaluated per the policy, rather than 

evaluated per pre-DPS-Policy 

documents. 

Natural Occurrence of a Taxon 

Abundant Elsewhere as an Introduced 

Population 

As stated in the DPS Policy, the 

Service believes that 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 of its 

historic range may be an indication that 

a population segment represents a 

significant resource warranting 

conservation under the Act (61 FR 

4724). However, the Sonoran Desert 

Area population does not represent the 

only surviving natural occurrence of the 

bald eagle throughout the range of the 

taxon in North America. 

Genetic Characteristics 

As stated in the DPS Policy, the 

Service believes that evidence that the 

discrete population segment differs 

markedly from other populations of the 

species in its genetic characteristics may 

be an indication that a population 

segment represents a significant 

resource warranting conservation under 

the Act (61 FR 4724). Hunt et al. (1992, 

pp. E–96 to E–110) contains the genetic 

work completed to date on the Arizona 

bald eagle population. Hunt et al. (1992, 

pp. A150–A165) suggested that the 

desert Arizona population, which 

includes the majority of bald eagles in 

the Sonoran Desert Area, may be 

reproductively isolated. Vyse (1992, p. 

E–100, E–101) notes that the results 

obtained could easily be explained by 

sampling procedures, and Zegers et al. 

(1992, pp. E–106 to E–109) question the 

reliability of the results because of the 

low numbers of individuals sampled 

from most States and because of the few 

loci examined. In conclusion, neither 

enzyme electrophoresis nor DNA 

fingerprinting resolved any specific 

genetic markers with which Arizona 

eagles could be differentiated from other 

populations. 

The available genetic studies on bald 

eagles are dated; the sample size was 

small; and researchers conducting the 

studies found the results to be 

inconclusive. As discussed above, 

eagles in the Sonoran Desert Area do not 

display any biologically distinctive 

traits that likely signal any unique 

genetic characteristics. Therefore, given 

the assumptions and cautions in using 

the data, we have determined that the 

best available data do not support a 

conclusion that bald eagles in the 

Sonoran Desert Area have genetic 

characteristics that are markedly 

different from other bald eagles. 

DPS Conclusion 

On the basis of the best available 

information, we conclude that the 

Sonoran Desert Area population of the 

bald eagle is discrete, but it is not 

significant in relation to the remainder 

of the taxon (i.e., bald eagles in North 

America). We believe the best scientific 

information provides substantial 

information on natal site fidelity in 

breeding birds and the limited number 

of other eagles in neighboring 

southwestern States. Further, we believe 

the results of the 30 years of monitoring 

data provide substantial information 

indicating that few, if any, eagles 

immigrate to or emigrate from the 

Sonoran Desert Area bald eagle 

population. These three factors lead us 

to conclude that the best available 

scientific information with respect to 

the discreteness requirements of the 

DPS Policy warrant considering the 

Sonoran Desert Area bald eagle 

population as discrete from other bald 

eagle populations in North America. 

Although they do persist in a arid 

region with high heat, as discussed 

above, Sonoran Desert Area bald eagles 

do not appear to express any 

adaptations that are not found in bald 

eagles elsewhere or that a population 

persisting in the Sonoran Desert Area 

will significantly increase the resiliency 

of the taxon as a whole. The adaptability 

of the bald eagle allows its distribution 

to be widespread throughout the North 

American continent in a variety of 

habitat types. We considered the four 

classes of information listed in the DPS 

Policy as possible considerations in 

making a determination as to 

significance; we also considered all 

other information that might be relevant 

to making this determination for the 

Sonoran Desert Area population. We 

conclude that the discrete Sonoran 

Desert Area population of bald eagle 

does not meet the significance criteria of 

the DPS Policy, as detailed above, and, 

therefore, is not a DPS pursuant to our 

DPS Policy. As a result, the Sonoran 

Desert Area population of bald eagles is 

not a listable entity under section 3(16) 

of the Act. 

Since we found that the population 

segment did not meet the significance 

element and, therefore, does not qualify 

as a DPS under the Service’s DPS 

Policy, we will not proceed with an 

evaluation of the status of the 

population segment under the Act. 

We note that, although we have 

determined that this portion of the range 

is not significant for the purposes of 

section 4 of the Act, we recognize that 

the bald eagles in the Sonoran Desert 

Area have great importance to people in 

this region, particularly Native 

Americans, and will continue to be 

protected under the BGEPA. We will 

continue to work with the States, Tribes, 

and conservation organizations in this 

region to conserve the bald eagle in the 

Sonoran Desert Area. 

Finding 

In making this finding, we considered 

information provided by the petitioners, 

as well as other information in our files, 

and otherwise available. We reviewed 

the petition, information submitted by 

the public and the Tribes, and available 

published and unpublished scientific 

and commercial information. We also 

consulted with Federal, State, and 

Tribal land managers, along with 

recognized experts in conservation and 

bald eagle biology. This 12-month 

finding reflects and incorporates 

information that we received from the 

public and through consultation, 

literature research, and field visits. 

Based on the rationale detailed above, 

we find that bald eagles in the Sonoran 

Desert Area constitute a discrete 

population segment. 

However, on the basis of our review, 

we find that the best scientific and 

commercial information does not 

indicate that the Sonoran Desert Area 

bald eagle constitutes a valid DPS, 

pursuant to the DPS Policy (61 FR 

4722). As described above, we believe 

the population to be discrete, but have 

determined that the Sonoran Desert 

Area bald eagle is not significant in 

relation to the remainder of the taxon 

(i.e. bald eagles in North America). 

Therefore, we conclude that the 

Sonoran Desert Area population is not 

a listable entity pursuant to section 

3(15) of the Act. Finally, we find that 

the Sonoran Desert Area portion of the 

range of the bald eagle in North America 

does not constitute a significant portion 

of the species’ range as this portion does 

not contribute meaningfully to the 

representation, resiliency, or 

redundancy of the entire taxon. 


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We encourage interested parties to 

continue to gather data that will assist 

with the conservation of the species. If 

you wish to provide information 

regarding the bald eagle, you may 

submit your information or materials to 

the Field Supervisor, Arizona Ecological 

Services Office (see ADDRESSES section 

above). The Service continues to 

strongly support the cooperative 

conservation of the Sonoran Desert Area 

bald eagle. 

On March 6, 2008, the U.S. District 

Court for the District of Arizona 

enjoined our application of the July 9, 

2007 (72 FR 37346), final delisting rule 

for bald eagles to the Sonoran Desert 

population pending the outcome of our 

status review and 12-month petition 

finding. As a result, we put this 

population back on the List of 

Threatened and Endangered Species on 

May 1, 2008. In light of our 12-month 

finding presented above, we intend to 

publish a separate notice to remove this 

population from the List of Threatened 

and Endangered Wildlife. However, we 

will only do so once the U.S. District 

Court for the District of Arizona has 

confirmed that its injunction, which 

required us to add this population to the 

List of Threatened and Endangered 

Wildlife, has been dissolved. Until that 

time, the Sonoran Desert Area 

population will remain protected by the 

Act. 

References Cited 

A complete list of all references cited 

herein is available, upon request, from 

the Arizona Ecological Services Office 

of the U.S. Fish and Wildlife Service 

(see ADDRESSES section above). 

Author 

The primary authors of this notice are 

the staff of the Arizona Ecological 

Services Office (see ADDRESSES). 

Authority 

The authority for this action is the 

Endangered Species Act of 1973, as 

amended (16 U.S.C. 1531 et seq.). 

Dated: February 17, 2010. 

Hannibal Bolton, 

Acting Director, Fish and Wildlife Service. 

[FR Doc. 2010–3794 Filed 2–24–10; 8:45 am] 

BILLING CODE 4310–55–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS–R1–ES–2008–0128] 

[MO 92210–0–0009–B4] 

RIN 1018–AW72 

Endangered and Threatened Wildlife 

and Plants; Withdrawal of Proposed 

Rule To List the Southwestern 

Washington/Columbia River Distinct 

Population Segment of Coastal 

Cutthroat Trout (Oncorhynchus clarki 

clarki) as Threatened 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Proposed rule; withdrawal. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), have 

determined that the proposed listing of 

the Southwestern Washington/Columbia 

River Distinct Population Segment 

(DPS) of coastal cutthroat trout as a 

threatened species under the 

Endangered Species Act of 1973, as 

amended (Act), is not warranted. We 

therefore withdraw our proposed rule 

(64 FR 16397; April 5, 1999) to list the 

DPS under the Act. Although we had 

earlier concluded that this DPS did not 

warrant listing under the Act, as a result 

of litigation we have reconsidered 

whether the marine and estuarine areas 

of the DPS may warrant listing if they 

constitute a significant portion of the 

range of the DPS. Based upon a 

thorough review of the best available 

scientific and commercial data, we have 

determined that the threats to coastal 

cutthroat trout in the marine and 

estuarine areas of its range within the 

DPS, as analyzed under the five listing 

factors described in section 4(a)(1) of the 

Act, are not likely to endanger the 

species now or in the foreseeable future 

throughout this portion of its range. We, 

therefore, again withdraw our proposed 

rule, as we have determined that the 

coastal cutthroat trout is not likely to 

become endangered now or in the 

foreseeable future throughout all or a 

significant portion of its range within 

the Southwestern Washington/Columbia 

River DPS. 

ADDRESSES: This withdrawal and 

supporting documentation are available 

on the Internet at http:// 

www.regulations.gov; search for Docket 

Number [FWS–R1–ES–2008–0128]. 

Supporting documentation for this 

determination is also available for 

inspection, by appointment, during 

normal business hours at the U.S. Fish 

and Wildlife Service, Oregon Fish and 

Wildlife Office, 2600 SE. 98th Avenue, 

Suite 100, Portland, OR 97266; 

telephone 503–231–6179; facsimile 

503–231–6195. 

FOR FURTHER INFORMATION CONTACT: Paul 

Henson, Ph.D., State Supervisor, U.S. 

Fish and Wildlife Service, Oregon Fish 

and Wildlife Office (see ADDRESSES, 

above). Persons who use a 

telecommunications device for the deaf 

(TDD) may call the Federal Information 

Relay Service (FIRS) at 800–877–8339. 

SUPPLEMENTARY INFORMATION: 

Background 

On July 5, 2002, we published a 

notice of our withdrawal of the 

proposed rule to list the Southwestern 

Washington/Columbia River distinct 

population segment (DPS) of the coastal 

cutthroat trout (Oncorhynchus clarki 

clarki) as threatened under the 

Endangered Species Act of 1973, as 

amended (Act) (67 FR 44934; July 5, 

2002). As a result of litigation, we are 

required to reconsider our withdrawal 

of the proposed rule with specific regard 

to the question of whether marine and 

estuarine areas may constitute a 

significant portion of the range of the 

Southwestern Washington/Columbia 

River DPS of coastal cutthroat trout. 

On March 24, 2009, we published a 

notice of reopening of a comment period 

on the proposed rule (74 FR 12297). In 

that notice, we alerted the public, other 

concerned governmental agencies, the 

scientific community, industry, and any 

other interested party of our request for 

information, data, or comments on the 

marine and estuarine areas of the 

Southwestern Washington/Columbia 

River DPS of coastal cutthroat trout, 

with particular regard to whether these 

areas constitute a significant portion of 

the range of the DPS under the Act, and 

if so, whether the subspecies is 

threatened or endangered in those areas. 

The comment period closed on April 

23, 2009, and we received four comment 

letters. After analyzing the information 

received, information in our files, and 

all other available information, we 

analyzed the threats to coastal cutthroat 

trout in the marine and estuarine 

portion of the DPS to determine whether 

coastal cutthroat trout are threatened or 

endangered in that area and, if so, 

whether the area constitutes a 

significant portion of the range of the 

DPS. Although the Court did not ask us 

to revisit status, trends, and threats to 

anadromous cutthroat trout or other lifehistory forms outside of marine and 

estuarine areas, we have also considered 

any new information available for these 

areas that would suggest any significant 

change in status, trend, or threats for the 


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