Federal Register / Vol. 71, No. 168 / Wednesday, August 30, 2006 / Proposed Rules 51549 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

Endangered and Threatened Wildlife 

and Plants; Petition to List the 

Sonoran Desert Population of the Bald 

Eagle as a Distinct Population 

Segment, List that Distinct Population 

Segment as Endangered, and 

Designate Critical Habitat 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Notice of 90-day petition 

finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce a 

90-day finding on a petition to reclassify 

the Sonoran Desert population of the 

bald eagle (Haliaeetus leucocephalus) in 

central Arizona and northwestern 

Mexico as a distinct population 

segment, list that distinct population 

segment as endangered, and designate 

critical habitat for that distinct 

population segment under the 

Endangered Species Act of 1973, as 

amended (Act). On the basis of a review 

of the information contained within the 

petition, we find that the petition does 

not provide substantial scientific or 

commercial information indicating that 

the petitioned action may be warranted. 

Therefore, we will not initiate a further 

status review in response to this 

petition. We ask the public to submit to 

us any new information that becomes 

available concerning the status of this 

population of the bald eagle or threats 

to it. 

DATES: The finding announced in this 

document was made on August 29, 

2006. 

ADDRESSES: The complete file 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. 

FOR FURTHER INFORMATION CONTACT: 

Steve Spangle (see ADDRESSES); 

telephone, 602–242–0210; facsimile, 

602–242–2513. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(A) of the Endangered 

Species Act of 1973, as amended (16 

U.S.C. 1531 et seq.) (Act), requires that 

we make a finding on whether a petition 

to list, delist, or reclassify a species 

presents substantial scientific or 

commercial information to indicate that 

the petitioned action may be warranted. 

We are to base this finding on 

information provided in the petition. To 

the maximum extent practicable, we are 

to make this finding within 90 days of 

our receipt of the petition, and publish 

our notice of this finding promptly in 

the Federal Register. 

Our standard for substantial 

information within the Code of Federal 

Regulations (CFR) with regard to a 90- 

day petition finding is ‘‘that amount of 

information that would lead a 

reasonable person to believe that the 

measure proposed in the petition may 

be warranted’’ (50 CFR 424.14(b)). If we 

find that substantial information was 

presented, we are required to promptly 

commence a review of the status of the 

species, if one has not already been 

initiated under our internal candidate 

assessment process. 

In making this finding, we relied on 

information provided by the petitioners 

and evaluated that information in 

accordance with 50 CFR 424.14(b). Our 

process of coming to a 90-day finding 

under section 4(b)(3)(A) of the Act and 

§ 424.14(b) of our regulations is limited 

to a determination of whether the 

information in the petition meets the 

‘‘substantial information’’ threshold. 

On October 6, 2004, we received a 

formal petition, dated October 6, 2004, 

from the Center for Biological Diversity 

(Center), the Maricopa Audubon 

Society, and the Arizona Audubon 

Council requesting that the bald eagle 

population found in the Sonoran Desert 

(as defined by Brown 1994) or, 

alternately, in the upper and lower 

Sonoran Desert (as defined by Merriam) 

be classified as a distinct population 

segment (DPS) and this DPS be 

reclassified as an endangered species, in 

accordance with the Act. The petition 

also requested that critical habitat be 

designated concurrently for the DPS. 

Because the Sonoran Desert described 

by Brown (1994) encompasses a 

different geographic area than that 

defined as upper and lower Sonoran 

Desert by Merriam, the Service 

requested clarification on the intended 

geographic boundaries for the Sonoran 

population on February 11, 2005. The 

petitioners responded with clarification 

on March 5, 2005, requesting that we 

consider in the DPS analysis those bald 

eagles nesting along riparian areas in the 

Sonoran Desert in Arizona and 

northwestern Mexico. At that time, 

further action on this petition was 

precluded by higher listing priorities. 

On January 19, 2006, we received from 

the Center a 60-day Notice of Intent 

(NOI) to sue the Service for failure to 

respond to the petition within the 

statutory timeframe. On March 27, 2006, 

the Center and the Maricopa Audubon 

Society filed a lawsuit against the U.S. 

Department of the Interior (DOI) and the 

Service for failure to make a finding on 

the petition within 90 days. 

Species Information 

The bald eagle (Haliaeetus 

leucocephalus) is the only species of sea 

eagle native to North America. Literally 

translated, H. leucocephalus means 

white-headed sea eagle (USFWS 1995, 

p. 36000). Bald eagles are birds of prey 

of the Order Falconiformes and Family 

Accipitridae. Bald eagles vary in length 

from 28 to 38 inches (71 to 97 

centimeters), weigh between 6.5 to 14 

pounds (2.9 to 6.4 kilograms), and have 

a 66 to 96 inch (1.8 to 2.6 meter) 

wingspan (Arizona Game and Fish 

Department (AGFD) 1999, p. 3). 

Distinguishing features include a yellow 

hooked bill and yellow unfeathered legs 

and feet. Adults of the species have a 

dark brownish-black body color, black 

talons, and a white head, neck, and tail. 

Immature bald eagles are mostly dark 

brown and lack a white head and tail 

until they reach approximately 5 years 

of age (AGFD 2006, pg. 3). 

Gerrard and Bartolotti (1988, p. 2) 

note that bald eagles are believed to 

have nested on both coasts, along all 

major rivers and large lakes in the 

interior from Florida to Baja California 

in the south, and north to Labrador and 

Alaska. The species is known to have 

bred in every State and province in the 

United States and Canada except Hawaii 

(Hunt et al. 1992, p. A–9). 

Hunt et al. (1992, pp. A–11 and A–12) 

summarized the earliest records from 

the literature for bald eagles in Arizona. 

Coues noted bald eagles in the vicinity 

of Fort Whipple in 1866 (now Prescott), 

and Henshaw reported bald eagles south 

of Fort Apache in 1875. Bent 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. 

The bald eagle population of the 

Southwest Recovery Region, as 

identified in the final recovery plan for 

the species, reaches throughout 

Oklahoma and Texas west of the 100th 

meridian, all of New Mexico and 

Arizona, and the area of California 

bordering the Lower Colorado River 

(USFWS 1982, p. 1). The vast majority 


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of these breeding bald eagles are found 

within the State of Arizona. The 

occurrence of breeding bald eagles in 

the State of New Mexico is very limited 

(USFS 2004, p. 153). In 2001, the New 

Mexico Department of Game and Fish 

(NMDGF) reported the occurrence of 

four bald eagle nest sites, all on private 

lands, in New Mexico. 

Nationwide, bald eagles are known to 

nest primarily along seacoasts and 

lakeshores, as well as along banks of 

rivers and streams (Stalmaster 1987, p. 

120). In the Southwest, bald eagle 

breeding areas (BA) (eagle nesting sites 

and the area where eagles forage) are 

located in close proximity to a variety 

of aquatic sites, including reservoirs, 

regulated river systems, and freeflowing rivers and creeks. The term 

‘‘BA’’ is used to define eagle nesting 

sites and the area where they forage. In 

the Southwest, nests are placed mostly 

on cliff edges, rock pinnacles, and in 

cottonwood trees. However, artificial 

structures, junipers, pinyon pines, 

sycamores, willows, ponderosa pines, 

and snags of these trees also have 

supported eagle nests (AGFD 2006, p. 

4). 

In Arizona, the majority of nests are 

located in the Upper and Lower 

Sonoran Life Zones (zones of plant and 

animal life associated with a given 

elevation), including the riparian 

habitats and transition areas of both 

zones (Hunt et al. 1992, p. A–17). 

Representative vegetation of these life 

zones includes Arizona sycamore 

(Platanus wrightii), blue paloverde 

(Parkinsonia florida), cholla (Opuntia 

spp.), Fremont cottonwood (Populus 

fremontii), Gooding willow (Salix 

gooddingii), mesquite (Prosopis spp.), 

saguaro (Carnegiea gigantea), and 

tamarisk or salt cedar (Tamarix 

pentandra; an exotic species) (Brown 

1994, p. 200). 

Historical evidence to document bald 

eagles nesting in New Mexico is lacking, 

although unverified reports suggest one 

or two pairs may have nested in 

southwestern New Mexico prior to 

1928. In the mid-1980s, a pair 

established a territory in Colfax County 

in an area where bald eagles 

concentrated in winter, and in 1987, an 

active nest was discovered nearby 

which produced two fledglings that 

year. In 1988, an active nest was 

discovered in Sierra County, also in an 

area of wintering eagle concentration; 

the nest fledged one young that year. 

Through 1999, those two nests together 

fledged a minimum of 31 young, with 

Colfax County being one of the more 

productive nests in North America. 

Additional nesting activity was 

recorded elsewhere after the mid-1980s, 

always in areas of wintering 

concentrations, including in San Juan, 

Rio Arriba, Quay, and Sierra counties. 

However, in each instance, eagles built 

nests only to abandon the effort prior to 

egg laying; such ‘‘practice’’ nests are not 

uncommon among inexperienced 

adults. In 1998, two additional nests 

were discovered in Colfax County, and 

each fledged young in both 1998 and 

1999 (five young total) (Williams 2000, 

abstract). 

Bald eagles are long-lived bird 

species. Southwestern bald eagles are 

known to exceed 12 years of age 

(USFWS 1999, p. 36454; Hunt et al. 

1992, p. A–v). Bald eagles primarily eat 

fish, but they will also eat amphibians, 

reptiles, birds, small mammals, carrion 

(dead animals), and carcasses of large 

mammals (cows, elk, deer, etc.). Their 

food habits can change daily or 

seasonally, but when a choice is 

available, bald eagles invariably select 

fish over other prey. Bald eagles will 

scavenge, steal, or actively hunt to 

acquire food. Carrion constitutes a 

higher proportion of the diet for 

juveniles and subadults than it does for 

adult eagles. Bald eagles are primarily 

sit-and-wait hunters, perching in trees 

in order to detect available prey 

(Stalmaster 1987, p. 104). 

Eagles in the Southwest frequently 

construct nests on cliffs. By 1992, of the 

111 nest sites known, 46 were in trees, 

36 on cliffs, 17 on pinnacles, 11 in 

snags, and 1 on an artificial platform 

(Hunt et al. 1992, p. A–17). However, 

for breeding areas where both cliff and 

tree nests were available, one study 

found that cliff nests were selected 73 

percent of the time, while tree nests 

were selected 27 percent of the time 

(Hunt et al. 1992, p. A–17). 

Additionally, eagles nesting on cliffs 

were found to be slightly more 

successful in raising young to fledgling, 

though the difference was not 

statistically significant. Nests may be 

used year after year. Hunt et al. (1992, 

p. A–20) determined the mean diameter 

of nests was 5 feet (156 centimeters). 

Food strongly influences bald eagle 

productivity (Newton 1979, pp. 95–96, 

101–106; Hansen 1987, p. 1389). A 

female’s health in the months preceding 

egg laying can affect egg production, 

and the prey availability during the 

breeding cycle affects the survivorship 

of nestlings and post-fledging juveniles. 

Thus, any factor affecting the adults’

ability to acquire food can influence 

productivity and adult survivorship 

(Newton 1979, pp. 95–96, 101–106). The 

most common fish eaten in the 

Southwest are Sonora and desert 

suckers; channel and flathead catfish; 

common carp largemouth, smallmouth, 

yellow, and white bass; and black 

crappie. Less common are roundtail 

chub, green sunfish, bluegill, tilapia, 

and rainbow trout (USFWS 1982, p. 11; 

AGFD 1999, p. 6). Prey availability has 

decreased on the upper Salt River in 

Arizona. The introduction of predatory 

flathead catfish in the late 1970s nearly 

extirpated native fish populations. 

Flathead catfish, while available as bald 

eagle prey when smaller, grow to large 

sizes (up to 50 pounds, or 22.6 

kilograms) making them too large for a 

prey item. Flathead catfish populations 

have increased while other fish species 

have decreased (AGFD 2006, p. 19). 

Productivity for the four bald eagle BAs 

on the upper Salt River decreased from 

1.12 young per year per occupied BA in 

the 1980s to 0.29 young per occupied 

BA in the 1990s. 

Bald eagles in the Southwest establish 

their breeding territories in December or 

January and lay eggs in January or 

February, which is early compared to 

bald eagles in more northerly areas 

(Stalmaster 1987, p. 63). Hunt et al. 

(1992, p. C–16) indicate that this may be 

a behavioral adaptation so that chicks 

can avoid the extreme desert heat of 

midsummer and adults can take 

advantage of food resources for the 

rearing of eaglets. Young fledgling 

eagles can remain in their nest area 

though June, learning how to fly and 

land, while still being primarily fed by 

adult eagles (Hunt et al. 1992, pp. C–6 

and C–7). 

About 45 days after leaving the nest, 

young southwestern bald eagles migrate 

to Canada, northern California, Idaho, 

Montana, North and South Dakota, 

Oregon, Washington, and Wyoming 

(Hunt et al. 1992, pp. A–104 through A–

114), returning to Arizona in the fall of 

the same year. They are known to repeat 

this behavior for a minimum of 2 years 

(Hunt et al. 1992a–112; p. A–122–A–

123). Resident adult bald eagles often 

stay in their BAs year-round, although 

local, short-term migrations are common 

(AGFD 1999, p. 6). 

The first major decline in bald eagle 

populations began in the mid- to late1800s, when widespread shooting for 

feathers and trophies led to extirpation 

of eagles in some areas. Carrion treated 

with strychnine, thallium sulfate, and 

other poisons were used as bait to kill 

livestock predators and ultimately killed 

many eagles as well. These and other 

factors contributed to a reduction in 

bald eagle numbers through the 1940s 

(USFWS 1999, p. 36455). In the late 

1940s, the use of dichloro-diphenyltrichloroethane (DDT) and other 

organochlorine compounds became 

widespread. While DDT was initially 

sprayed along coastal and other wetland 


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areas for mosquito control, it later was 

used as a general crop insecticide. DDT 

accumulated in individual bald eagles 

that had ingested contaminated prey, 

and reproductive success plummeted 

(USFWS 1999, p. 36455). In the late 

1960s and early 1970s, it was 

determined that dichlorophenyldichloroethylene (DDE), a breakdown 

product of DDT, accumulated in fatty 

tissues of adult female eagles and 

impaired the calcium release needed for 

normal egg shell formation. 

On March 11, 1967 (32 FR 4001), the 

Secretary of the Interior listed bald 

eagles south of the 40th parallel 

(latitudinal line running roughly from 

northern California to New Jersey) as 

endangered under the Endangered 

Species Preservation Act of 1966 (16 

U.S.C. 668aa–668cc). On December 31, 

1972, DDT was banned from use in the 

United States by the Environmental 

Protection Agency. 

Nationwide bald eagle surveys 

conducted in 1973 and 1974 revealed 

the declining trend of bald eagle 

population numbers throughout the 

lower 48 States. We responded by 

listing the bald eagle throughout the 

lower 48 States as endangered except in 

Michigan, Minnesota, Wisconsin, 

Washington, and Oregon, where the 

bald eagle was designated as threatened 

(43 FR 6233, February 14, 1978). 

Nesting populations of bald eagles have 

more recently been increasing 

throughout the United States. Data from 

surveys conducted between 1963 and 

1998 show that known active nest sites 

in the lower 48 States have grown from 

417 to over 5,748 occupied BAs 

(USFWS 1995, p. 36001; USFWS 1999, 

p. 36457). Today, the Service estimates 

the population in the lower 48 states to 

be at approximately 7,066 breeding 

pairs (USFWS 2006, p. 8239). 

The 1982 recovery plan for the 

Southwestern Recovery Region states 

that when the total reproduction for the 

eagle population within the 

Southwestern Recovery Region as a 

whole has effectively doubled to 10–12 

young per year over a 5-year period, and 

the population range has expanded to 

include one or more river drainages in 

addition to the Salt and Verde River 

Systems, the southwestern bald eagle 

should be reclassified to threatened. The 

1982 recovery plan indicated that 

Arizona was the only State in the 

recovery region containing nesting bald 

eagles, with 42 unverified historical 

nesting territories in the Salt and Verde 

River systems, and one occupied 

territory along the Colorado River. As 

discussed in the February 16, 2006, 

Federal Register notice reopening the 

comment period on the proposed rule to 

delist the bald eagle through its range 

(71 FR 8238), the downlisting goal 

established in the recovery plan for the 

southwestern bald eagle has been 

exceeded. Further, on July 12, 1995, we 

reclassified the bald eagle from 

endangered to threatened in the lower 

48 States (60 FR 36000). 

The number of known BAs has 

increased from a low of 3 in 1971, to a 

high of 50 in 2006, while the number of 

occupied BAs increased from a low of 

3 in 1971, to a high of 43 in 2006. The 

number of young hatched increased 

from a low of 0 in 1972, to a high of 55 

in 2006 (AGFD 2006, pp. 48–49; AGFD 

unpubl. data 2006). Productivity has 

also changed. Between 1975 and 1984, 

average productivity was 0.95 young per 

occupied BA. Between 1987 and 2005, 

average productivity was 0.78 young per 

occupied BA. These data take into 

account productivity for BAs 

throughout the Southwest, and they are 

not restricted to the Sonoran Desert 

population of bald eagles evaluated 

under the petition. 

While the number of BAs has 

increased, there was no expectation that 

these BAs would demonstrate a 

corresponding increase in reproductive 

performance. In part, this is because 

early monitoring detected BAs with the 

highest quality habitat that were easily 

discovered. Following an intensive 

survey effort, we now know of more 

BAs, but habitat conditions within them 

ranges from poor to excellent. As a 

result, we are now tracking productivity 

in BAs with a variety of habitat 

conditions, rather than tracking 

productivity in only those BAs that 

were easily detected and were in prime 

habitat. The result of having more 

thorough, representative data from more 

BAs in a variety of habitat types is that 

we show fewer ‘‘boom and bust’’ years. 

Productivity data between 1987 and 

2005 indicates a more stabilized 

performance. For example, in 1971, 

with only three known BAs, 

productivity was 1.33. In 1972, with the 

same number of known BAs, 

productivity was 0.0. In 1973, 

productivity was at 1.5. By comparison, 

with more BAs known, productivity 

fluctations now typically vary by only 

0.20 to 0.30 (AGFD 2006, pp. 48–49; 

AGFD unpubl. data 2006). 

AGFD (2006c, p. 5) additionally notes 

that the change in productivity could be 

due to a difference in monitoring 

protocols. More importantly, they note 

that an average productivity rate of 0.78 

young/occupied breeding area is 

consistent with the range of many other 

areas in the species range with larger 

bald eagle populations, including 

Minnesota, British Columbia, Interior 

Alaska, and Washington. 

For the Sonoran Desert population of 

bald eagles (i.e., excluding those BAs 

not considered within the area of 

analysis under this action), the number 

of occupied BAs increased from a low 

of 3 in 1971 to a high of 36 in 2004. 

Productivity for only those BAs within 

the Sonoran Desert population is that 

same as that for the southwestern 

population up until 1994, when BAs 

outside of the Sonoran Desert 

population were discovered. From 1994 

forward, productivity within the 

Sonoran Desert population has ranged 

between 0.62 and 1.06, reaching a high 

in 2004. Productivity remained high at 

1.01 young per occupied BA for 2005 

(AGFD 2004a, p. 15; AGFD 2004, p. 6; 

AGFD 2005, p. 7; AGFD 2006, Table 7, 

pp. 48–50). The average annual 

productivity for this time period is at 

0.78, which corresponds to that for the 

overall southwestern population. 

Previous Federal Actions 

On March 11, 1967 (32 FR 4001), bald 

eagles south of 40 degrees north latitude 

were federally listed as an endangered 

species. Bald eagles north of this line 

were not listed at that time because 

those populations had not experienced 

the same threats and population 

declines as of 1967. On February 14, 

1978, we listed the bald eagle as 

endangered in 43 States, and threatened 

in 5 others (43 FR 6233). Bald eagles 

were not listed in Alaska, and are not 

found in Hawaii. On July 12, 1995, we 

reclassified the bald eagle from 

endangered to threatened in the lower 

48 States (60 FR 36000). The bald eagle 

remained classified as threatened in 

Michigan, Minnesota, Wisconsin, 

Oregon, and Washington, as originally 

listed. 

On July 6, 1999, we proposed to 

remove the bald eagle from the List of 

Endangered and Threatened Wildlife in 

the lower 48 States, including the 

Southwest Recovery Region (64 FR 

36454). The original comment period 

was open for 90 days, until October 5, 

1999. We reopened the comment period 

on that proposal on February 16, 2006 

(71 FR 8238), for an additional 90 days, 

until May 17, 2006, and we extended 

the comment period on May 16, 2006 

(71 FR 28369), for another 30 days, until 

June 19, 2006. 

Distinct Vertebrate Population Segment 

We consider a species for listing 

under the Act if available information 

indicates such an action might be 

warranted. ‘‘Species’’ is defined by the 

Act as including any species or 

subspecies of fish and wildlife or plants, 


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and any distinct vertebrate population 

segment of fish or wildlife that 

interbreeds when mature (16 U.S.C. 

1532(16)). We, along with the National 

Marine Fisheries Service (now the 

National Oceanic and Atmospheric 

Administration—Fisheries), developed 

the Policy Regarding the Recognition of 

Distinct Vertebrate Population Segments 

(DPS policy) (61 FR 4722, February 7, 

1996), to help us in determining what 

constitutes a DPS. The policy identifies 

three elements that are to be considered 

in a decision regarding the status of a 

possible distinct population segment 

(DPS). These elements include (1) the 

discreteness of the population in 

relation to the remainder of the species 

to which it belongs; (2) the significance 

of the population segment to the species 

to which it belongs; and (3) the 

population segment’s conservation 

status in relation to the Act’s standards 

for listing. Our policy further recognizes 

it may be appropriate to assign different 

classifications (i.e., threatened or 

endangered) to different DPSs of the 

same vertebrate taxon (61 FR 4721; 

February 7, 1996). 

In the Service’s final rule reclassifying 

the bald eagle from endangered to 

threatened (July 12, 1995, 60 FR 36000), 

we determined that eagles in the 

Southwestern Recovery Region were 

part of the same bald eagle population 

as that of the remaining lower 48 States, 

and we determined it was appropriate to 

include it in the reclassification. 

However, the petition requests action 

with respect to an area (i.e., Sonoran 

Desert) that differs from the area that 

was analyzed in the reclassification rule 

(i.e., Southwestern Recovery 

Region),and provides new information 

not considered in 1995. 

Discreteness 

The DPS policy states that a 

population segment of a vertebrate 

species may be considered discrete if it 

satisfies either one of the following two 

conditions: It must be markedly 

separated from other populations of the 

same taxon as a consequence of 

physical, physiological, ecological, or 

behavioral factors, or it must be 

delimited by international boundaries 

within which significant differences in 

control of exploitation, management or 

habitat conservation status or regulatory 

mechanisms exist that are significant in 

light of section 4(a)(1)(D) of the Act. Our 

evaluation of discreteness under the 

DPS policy, based on information 

provided in the petition and available in 

our files, is presented below. 

Discreteness Criteria 1. The Population 

Segment 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 

Ecological Factors 

The petition notes the geographic 

region occupied by Sonoran Desert bald 

eagles is much drier and hotter than that 

of any other bald eagle population, and 

represents a significant departure from 

the habitat selected by bald eagles in the 

rest of North America. The petition 

concludes that, in order to adapt to high 

summer temperatures and to time 

breeding cycles to the accessibility and 

spawn of native fish (primarily suckers), 

Sonoran Desert bald eagles breed earlier, 

nest earlier, and fledge their young 

sooner than bald eagles elsewhere 

(AGFD 1999a, 2000; Gerrard and 

Bortolotti 1988; Hunt et al. 1992; 

Stalmaster 1987; USFWS 2003b). In 

addition, the petition notes that, unlike 

bald eagles elsewhere in North America, 

Sonoran Desert bald eagles use cliff nest 

sites and that 53 of 111 known nests, or 

48 percent, are on cliffs or pinnacles. 

They further note the only other place 

this occurs is in the Aleutian Islands 

(Hunt et al. 1992). 

Response to the Petition 

The information provided in the 

petition on behavioral adaptations to the 

Sonoran Desert is, in part, accurate. 

While it is true that Sonoran Desert bald 

eagles initiate nesting earlier than eagles 

in some parts of the country, Stalmaster 

(1987, p. 63) notes bald eagles in Florida 

initiate breeding activities in October, 

even earlier than Arizona bald eagles. 

Florida bald eagles also lay eggs earlier 

(Stalmaster 1987, p. 63; Gerrard and 

Bortolotti 1988 p. 76). Accordingly, 

Florida bald eagles hatch and fledge 

earlier than those in Arizona. Stalmaster 

(1987, p.63) concludes timing of various 

breeding events is tied to latitude of the 

nesting area, with eagles at more 

northern latitudes breeding at later 

dates. 

With respect to cliff nesting, the 

information presented on the use of cliff 

nests is accurate. However, this is not 

necessarily a unique trait of Sonoran 

Desert bald eagles. Gerrard and 

Bortolotti (1988, p. 41) note bald eagles 

in other areas may nest on cliffs if 

suitable trees are not available. 

Stalmaster (1987) noted exceptions to 

tree nests as well, but indicated that, 

while eagles in other areas may rarely 

use cliffs or other surfaces, this is an 

exception, whereas in Arizona, cliff 

nesting is common. In addition, bald 

eagles are known to nest on cliffs on the 

Channel Islands off California (Montrose 

Settlements Restoration Program 2005). 

Behavioral Factors 

The petition provides information 

alleging that the Sonoran Desert bald 

eagles are reproductively isolated. 

Specifically, the petition contends that 

352 out of 353 individuals (99.997 

percent) objectively identified while 

participating in breeding activity in this 

population came from within the 

Sonoran Desert bald eagle population. 

Additionally, the petition notes that, 

since 1977, biologists in Arizona have 

banded 256 nestlings with only one 

individual identified as having 

emigrated. According to the petition, 

this indicates that 99.6 percent of 

individuals born into the Sonoran 

Desert remain in the desert (AGFD 

1999a, 2000). The petition states that, to 

date, evidence from the banding and 

identification of breeding adults 

supports the hypothesis that the 

Sonoran Desert bald eagle breeding 

population is not supported or 

maintained by immigration from other 

states or regions. They quote AGFD 

(1999a, 2000): 

‘‘[B]ecause adults return to the vicinity of 

their natal area to breed, the large distance 

between small breeding populations in the 

Southwest decreases the chance for 

movement between neighboring populations. 

Probably most convincing are the results 

from banding 256 nestlings over 20 years and 

identifying 372 breeding adults over 8 years. 

Only one individual from out-of-state entered 

the breeding population and only one left. 

Additionally, the proportion of breeding 

adults with color bands had steadily 

increased, while the presence of unmarked 

Bald Eagles has decreased. Thus, continued 

attention to the survivorship of all Arizona 

Bald Eagles is vital to the maintenance of our 

breeding population. We can not depend on 

immigration to Arizona from nearby states to 

make up for poor management in Arizona 

***’’

The petition claims the AGFD (1994b) 

warned that repopulation of the 

Sonoran Desert bald eagle population 

following a population crash would be 

highly unlikely, and quote the AGFD 

(1994b) as follows: 

‘‘Because Arizona continues to possess 

nearly the entire breeding population within 

the Southwestern Region, concerns remain 

over retaining the genetic integrity of this 

population * * * Should a population crash 

occur in Arizona, the pool of eagles to 

repopulate the Southwest could be left to the 

few pairs in the neighboring states or Mexico. 

However, at this time, there is no 

documentation of eagles from these 

neighboring Southwestern states breeding in 

Arizona or vice versa.’’


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The petition further states that natal 

site fidelity is common for bald eagles, 

noting that, in a study of nine bald eagle 

populations including thousands of 

banded birds, only two nestlings were 

found to have bred in other areas. One 

of these birds moved 331 kilometers 

(205 miles) north from its natal site in 

the Greater Yellowstone Ecosystem 

(Harmata in litt.) while the other 

traveled 418 kilometers (260 miles) 

south from its natal site near Charleston, 

South Carolina (T. Murphy, pers. 

comm., Wood in litt.). They conclude 

that the tendency for banded nestlings 

to breed within their natal populations 

is well known (Hunt et al. 1992). 

Response to the Petition 

The information in the petition 

appears to be accurate and reliable; 

however, it should be noted the only 

individual cited as entering the breeding 

population from out-of-state refers to a 

bald eagle from Texas (AGFD 2006, p. 

27) that currently occupies the Luna BA, 

which is not part of the Sonoran Desert 

bald eagle population. As a result, the 

appropriate conclusion is all birds 

objectively identified while 

participating in breeding activity in the 

Sonoran Desert bald eagle population 

came from within the population. It 

should also be noted that sub-adult bald 

eagles do migrate and return annually. 

As noted above, about 45 days after 

leaving the nest, young southwestern 

bald eagles migrate to Canada, northern 

California, Idaho, Montana, North and 

South Dakota, Oregon, Washington, and 

Wyoming (Hunt et al. 1992, p. A–104—

A–114), returning to Arizona in the fall 

of the same year. They are known to 

repeat this behavior for a minimum of 

2 years (Hunt et al. 1992a–112; p. A–

122—A–123). Resident adult bald eagles 

often stay in their BAs year-round, 

although local short-term migrations are 

common (AGFD 1999, p. 6). 

We agree with the petitioners that, 

should the Sonoran Desert bald eagle 

population experience a rapid decline, 

there are few eagles in neighboring 

southwestern states or Mexico which 

could serve as a source population for 

the Sonoran Desert bald eagle 

population. Finally, we find the 

information from Harmata et al. (1999, 

p. 788) and Hunt et al. (1992, p. A–144) 

supports the discussion on the natal 

origins of breeding adults, and the 

probability that adult bald eagle will not 

immigrate to the Sonoran Desert bald 

eagle population from surrounding 

southwestern states or farther. 

Evidence of Genetic Discontinuity 

With respect to genetic isolation, the 

petition found that the current 

understanding of genetics does not 

refute the discrete and isolated nature of 

the desert nesting bald eagle. The 

petition notes a review of all 

information regarding genetic analysis 

of the southwestern desert nesting bald 

eagle reveals consistent uncertainty, and 

concludes current genetic data support 

no definitive conclusions concerning 

isolation or lack of isolation (CBD 

2004e; Hunt et al. 1992; SWCBD 1999). 

The petition states that, while no 

definitive conclusions are supported by 

the limited genetic data, this is not 

required under the current DPS policy. 

Specifically, the petition quotes from 

the policy: 

‘‘Thus, evidence of genetic distinctness or 

of the presence of genetically determined 

traits may be important in recognizing some 

DPS’s, but the draft policy was not intended 

to always specifically require this kind of 

evidence in order for a DPS to be recognized 

***’’

Similarly, the petition notes absolute 

reproductive isolation is not required 

under the policy, which states: 

‘‘The Services do not consider it 

appropriate to require absolute reproductive 

isolation as a prerequisite to recognizing a 

distinct population segment. This would be 

an impracticably stringent standard, and one 

that would not be satisfied even by some 

recognized species that are known to sustain 

a low frequency of interbreeding with related 

species * * *’’

Response to the Petition 

The information presented within the 

petition on completed genetic studies 

for bald eagles appears accurate and 

reliable. Hunt et al. (1992, pp. E–96 to 

E–110) contains the genetic work 

completed to date on the southwestern 

bald eagle population. Vyse (1992, p. E–

100, E–101) notes the data are 

inconclusive, as evidenced by such 

statements as ‘‘These findings must be 

assumed to be preliminary (and treated 

with due caution), because of a lack of 

information concerning sampling 

procedures. The results we have 

obtained could easily be explained by 

sampling procedures’’; and ‘‘At present 

these data (HinfI/M–13) are too 

incomplete to be considered further.’’ In 

addition, Zegers et al. (1992, p. E–106 to 

E–109) notes that ‘‘Question 4 * * * is 

difficult to answer with precision 

because of the different sample sizes 

between 1985 and 1990. * * * [T]his 

difference is possibly an artifact of the 

many fewer samples in 1985’’; ‘‘six loci 

may not be enough to give a reliable 

estimate of the true genetic distance’; 

and ‘‘We feel caution should be 

exercised when interpreting these 

results due to the low numbers of 

individuals sampled from most states 

but especially because of the few loci 

examined.’’

Evidence of Morphological 

Discontinuity 

The term ‘‘morphological 

discontinuity’’ refers to some difference 

in physical characteristics that may 

exist between two groups. The petition 

contends that quantitative measures of 

the physical differences between 

Sonoran Desert bald eagles and bald 

eagles elsewhere offers evidence of 

morphological discontinuity. The 

petition cites quantitative measures of 

physical difference, stating that average 

weights of male bald eagles are 3.3 

kilograms (kg) (7.3 pounds (lbs.)) in 

Arizona, 4.1 kg (9.0 lbs.) in California, 

and 4.7 kg (10.4 lbs.) in Alaska. 

Similarly, average weight for females is 

4.5 kg (9.9 lbs.) in Arizona, 5.1 kg (11.2 

lbs.) in California, and 5.8 kg (12.8 lbs.) 

in Alaska (Hunt et al. 1992). 

Response to the Petition 

The information provided on size 

differences appears to be accurate and 

reliable, as found in Hunt et al. (1992, 

p. A–159). Stalmaster (1987, pp. 16–17) 

notes southern eagles are much smaller 

and lighter than their northern 

counterparts. This is consistent with 

Bergmann’s Rule, which holds that 

animal size increases with increasing 

latitude. Gerrard and Bortolotti (1988, p. 

14) note Florida birds are the smallest, 

with a gradation of small to large from 

south to north. The importance of this 

morphological difference and its 

potential isolating effects are discussed 

by Hunt et al. (1992, p. A–165), who 

notes morphological differences such as 

small size may be an adaptation related 

to desert conditions, noting a decision 

to release birds into Arizona from 

elsewhere should be considered only as 

a last resort, as the introduction of 

foreign genes into the Sonoran Desert 

population might disrupt coadapted 

gene complexes specific to the desert 

population. 

Discreteness Criteria 2. It is Delimited by 

International Government Boundaries 

Within Which Differences in Control of 

Exploitation, Management of Habitat, 

Conservation Status, or Regulatory 

Mechanisms Exist That are Significant 

in Light of Section 4(a)(1)(D) of the Act 

No specific information was 

identified in the petition for this 

category. Therefore we will not address 

this category in our analysis of 

discreteness. 

Conclusion 

We have reviewed the information 

presented in the petition, and have 


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evaluated the information in accordance 

with 50 CFR 424.14(b). On the basis of 

our review, we find available genetic 

studies on bald eagles are dated, the 

sample size was small, and researchers 

conducting the studies found the results 

to be inconclusive. We therefore believe 

that the best available genetic 

information is inconclusive with regard 

to the discreteness of the Sonoran Desert 

bald eagle population. However, we 

believe the petition presents substantial 

information on the Sonoran Desert bald 

eagles with respect to size. However, 

size in birds is known to be a clinal 

function of latitude and does not 

necessarily indicate discreteness. We 

believe the petition provides substantial 

information on natal site fidelity in 

breeding birds and the limited number 

of other eagles in neighboring 

southwestern states or Mexico. Finally, 

we believe the data indicating that 20 

years of monitoring have resulted in the 

determination that no eagles have 

immigrated to and only one eagle has 

emigrated from the Sonoran Desert bald 

eagle population is substantial. We, 

therefore, conclude that the petition 

contains substantial information with 

respect to the discreteness requirements 

of the DPS policy to warrant considering 

the Sonoran Desert bald eagle 

population as discrete from other bald 

eagle populations. 

Significance 

If we determine that a population 

segment is discrete under one of the 

above conditions, we must then 

consider its biological and ecological 

significance to the taxon to which it 

belongs, within the context that the 

Service’s authority to list DPSs be used 

‘‘sparingly’’ while encouraging the 

conservation of genetic diversity (61 FR 

4722; February 7, 1996). This 

consideration may include, but is not 

limited to the following: (1) Evidence of 

the persistence of the population 

segment in an ecological setting that is 

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. 

Significance Criteria 1. Persistence of 

the Population Segment in an Ecological 

Setting That Is Unusual or Unique for 

the Taxon 

Information Provided in the Petition 

The petition contends that the 

Sonoran Desert bald eagle persists in the 

unique ecological setting of the Sonoran 

life zones of the desert Southwest 

(AGFD 1999a, 2000; Hunt et al. 1992; 

USFWS 2002a, 2003b). With the 

exception of a single 8,000 foot (2,438 

meter) elevation nest (Luna BA), the 

petition states that all known Arizona 

BAs are located in the Sonoran Desert 

in the central part of the State in Upper 

and Lower Sonoran Desert habitats from 

elevations of 1,080 feet (330 meters) to 

5,640 feet (1,720 meters), and are closely 

associated with the Salt, Verde, and Gila 

river drainage waters (Beatty and 

Driscoll 1994, 1996a; Beatty et al. 1995a, 

1995b, 1998; Driscoll and Beatty 1994; 

Driscoll et al. 1992; Hunt et al. 1992). 

The petition further identifies several 

Arizona tree species native to the desert 

Southwest as representative vegetation 

for these areas (Brown 1994). 

Response to the Petition 

The breeding range of the bald eagle 

is associated with aquatic habitats 

(coastal areas, river, lakes, and 

reservoirs) with forested shorelines or 

cliffs in North America (Buehler 2000). 

The ecological setting in which the bald 

eagle persists in the Sonoran Desert may 

at first seem unusual for the species. 

However, despite the desert setting, bald 

eagles of the Sonoran Desert are 

consistently associated with preferred 

bald eagle habitat, the riparian 

ecosystem. The petition clearly states 

that the Sonoran Desert nests are closely 

associated with the Salt, Verde, and Gila 

river drainage waters and cites Brown 

(1994) when describing the riparian 

vegetation of these areas. As with all 

populations of bald eagles throughout 

the lower 48 States, suitable riparian 

habitat, or other comparable aquatic 

habitat, is an essential prerequisite to 

successful eagle reproduction in the 

desert Southwest (USFWS 1982). 

Riparian ecosystems occupied by 

nesting bald eagles in the Sonoran life 

zones of the desert Southwest, therefore, 

do not constitute a unique setting for the 

species. The persistence of the bald 

eagle in this setting likely represents an 

example of a species occupying the edge 

of its range of suitable habitats. 

Therefore, we conclude that the petition 

does not present substantial evidence 

that the population is persisting in an 

ecological setting that is unique for the 

taxon. 

Significance Criteria 2. Loss of the 

Population Segment Would Result in a 

Significant Gap in the Range of the 

Taxon 

Information Provided in the Petition 

The petition contends that for more 

than twenty years, the Service has 

recognized the fact that the Southwest 

represents a ‘‘significant portion of the 

bald eagle range’’ and further states that 

it follows logically then that the loss of 

the [Sonoran] Desert nesting population 

would result in a significant gap in the 

range of the bald eagle (Hunt et al. 1992; 

USFWS 1982, 1994a, 1995, 2001a). The 

petition claims that bald eagles in the 

Southwestern United States have been 

considered as a distinct population for 

the purposes of consultation and 

recovery efforts under the Act (USFWS 

2003b). 

The petition further contends that 

several authors have speculated about 

the consequences of this population’s 

loss (AGFD 1994b; Hunt et al. 1992), 

and the petitioners can find no credible 

evidence that bald eagles elsewhere 

possess the ability to adapt to the 

unique and hostile environmental 

habitat in which the [Sonoran] Desert 

nesting population has evolved. 

Specifically the petition quotes Hunt et 

al. (1992): 

‘‘[W]ere the [Southwestern Desert Nesting 

Bald Eagle] population extirpated, there is no 

firm reason to believe that bald eagles 

released into Arizona from elsewhere would 

posses [sic] the adaptations required to 

increase their numbers.’’

The petition further quotes 

correspondence from the Arizona Game 

and Fish Department to the Service 

(1994b): 

‘‘Because Arizona continues to possess 

nearly the entire breeding population within 

the Southwestern Region, concerns remain 

over retaining the genetic integrity of this 

population. * * * Should a population crash 

occur in Arizona, the pool of eagles to 

repopulate the Southwest could be left to the 

few pairs in the neighboring states or Mexico. 

However, at this time, there is no 

documentation of eagles from these 

neighboring Southwestern States breeding in 

Arizona or vice versa.’’

Response to the Petition 

The petition cites several Service 

publications (1982, 1994a, 1995, 2001a) 

in addition to a report prepared by Hunt 

et al. (1992) when making this claim, 

but does not make specific reference to 

instances in which the Service has 

‘‘recognized the fact that the Southwest 

represents a significant portion of the 

Bald Eagle range.’’ Therefore, for this 

analysis we will assume that the 

petition is referring to the fact that the 


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Service has continued to identify the 

Southwest population of the bald eagle 

as one of five recovery populations in 

the lower 48 States for more than twenty 

years (Hunt et al. 1992; USFWS 1982, 

1994a, 1995, 2001a). 

In establishing a recovery program for 

the species in the mid-1970’s, the 

Service divided the bald eagles of the 

lower 48 States into five recovery 

populations, based on geographic 

location, termed Recovery Regions. This 

was as a result of the wide distribution 

of the bald eagle in the lower 48 States. 

Recovery plans were prepared for the 

five Recovery Regions, including the 

Southwest Recovery Region (USFWS 

1982), by separate recovery teams 

composed of species experts in each 

geographic area. The Service views the 

establishment of recovery regions as a 

management tool allowing for effective 

regional coordination and planning 

among State and Federal conservation 

agencies and species experts. The 

existence of a recovery region does not, 

in itself, imply significance under the 

DPS policy (USFWS and NMFS 1996), 

as the petitioner claims, and therefore 

the Southwestern Recovery Region is 

not a DPS for the purposes of recovery. 

In the 1994 proposed rule to reclassify 

the bald eagle from endangered to 

threatened (59 FR 35584; July 12, 1994), 

the Service determined that current 

information indicates the Southwestern 

population is at risk and remains in 

danger of extinction due to excessively 

low survival rates and the need for 

intensive management, particularly at 

nest sites. This decision was based on 

the understanding that the population 

was isolated and thus subject to the 

genetic, demographic, and 

environmental threats known to be 

associated with small populations. Data 

provided in the Hunt et al. (1992) 

publication indicated there had been no 

immigration to the Southwestern 

population of bald eagles. At that time 

the Service recognized the 

Southwestern Recovery Region as a DPS 

based on evidence that it appeared to be 

reproductively isolated (59 FR 35584; 

July 12, 1994). However, in the 1995 

final rule to reclassify bald eagles from 

endangered to threatened, the Service 

affirmed that the Southwestern 

Recovery Region of the bald eagle is not 

a DPS but instead part of the same bald 

eagle population as that of the 

remaining lower 48 States (USFWS 

1995). This determination was based on 

evidence of immigration into the 

population (USFWS 1995), interpopulation movements (Mabie et al. 

1994), and the then existing genetic 

data, which did not support the 

Service’s previous assertion that the 

bald eagles of the Southwestern 

Recovery Region are reproductively 

isolated (Hunt et al. 1992). 

On July 6, 1996, the Service and the 

National Marine Fisheries Service 

jointly published a policy that clarifies 

the Agencies’ interpretation of the 

phrase ‘‘distinct population segment of 

any species of vertebrate fish or 

wildlife’’ for the purposes of listing, 

delisting, and reclassifying species 

under the Act (USFWS and NMFS 

1996). The policy identifies three 

elements that are to be considered in a 

decision regarding the status of a 

possible distinct population segment 

(DPS). These elements include (1) the 

discreteness of the population segment 

in relation to the remainder of the 

species to which it belongs; (2) the 

significance of the population segment 

to the species to which it belongs; and 

(3) the population segment’s 

conservation status in relation to the 

Act’s standards for listing (USFWS and 

NMFS 1996). 

Subsequent to publication of the DPS 

policy, the Service published a 

proposed rule to remove the bald eagle 

in the lower 48 States from the list of 

endangered and threatened wildlife 

(USFWS 1999). On February 16, 2006 

the Service reopened the comment 

period for the proposed rule (USFWS 

2006). In both of these publications the 

Service recognized a single listed 

population of bald eagles throughout the 

lower 48 States as had been done in the 

earlier 1995 final rule (USFWS 1995), 

although a formal analysis consistent 

with the 1996 DPS policy had not been 

completed for the Southwestern 

Recovery Region (USFWS 1999, 2006). 

The petition is correct in that early 

biological opinions, as part of 

consultations with Federal action 

agencies under section 7 of the Act, 

finalized by the Arizona Ecological 

Services Office referred to the 

Southwestern population as a DPS. 

However, in the 1995 final rule to 

reclassify bald eagles from endangered 

to threatened (USFWS 1995), the 

Service affirmed that the Southwestern 

population of the bald eagle is not a 

DPS. Some biological opinions dated 

after the final rule note that the 

Southwestern population of the bald 

eagle was previously considered a DPS, 

but no longer is considered as such. In 

the February 16, 2006 reopening of the 

comment period for the proposed rule to 

delist the bald eagle, the Service further 

explains that when preparing biological 

opinions under section 7 of the Act the 

potential effects to the Southwestern or 

any of the other four recovery regions of 

the bald eagle are considered in terms 

of whether they appreciably reduce the 

likelihood of both survival and recovery 

of the bald eagle throughout the lower 

48 States, not solely for the geographic 

area in which the impacts may occur 

(USFWS 2006). Therefore, the bald 

eagles in the Southwestern United 

States are not considered as a distinct 

population for the purposes of 

consultation under the Act. Further, the 

petition under consideration in this 

finding requests action with respect to 

a geographic area (i.e., Sonoran Desert) 

that differs from the area that was 

analyzed in the Service’s reclassification 

rule (i.e., Southwestern Recovery 

Region) (USFWS 1995). In this context, 

claims regarding how the Service has 

referred to the Southwest Recovery 

Region are not relevant to the petitioned 

action. 

Finally, the bald eagle ranges 

throughout much of North America, 

nesting on both coasts from Florida to 

Baja California in the south, and from 

Labrador to the western Aleutian 

Islands, Alaska in the north (Gerrard 

and Bartolotti 1988). While the 

statements of two authors who have 

‘‘speculated’’ about the consequences of 

the Sonoran Desert population’s loss are 

accurately quoted, these statements do 

not specifically address how the loss of 

the Sonoran Desert bald eagle 

population would constitute a 

significant gap in the range of the 

species. Furthermore, the petitioner 

provides no supporting evidence to 

substantiate the authors’ speculations. 

We conclude that the bald eagles in 

the Southwestern United States are not 

considered as a distinct population for 

the purposes of consultation or 

recovery. Furthermore, the petition does 

no provide substantial information to 

support the claim that loss of the 

Sonoran Desert bald eagle population 

would result in a significant gap in the 

range of the species. 

Significance Criteria 3. The Population 

Segment Represents the Only Surviving 

Natural Occurrence of a Taxon That 

May Be More Abundant Elsewhere as an 

Introduced Population Outside Its 

Historical Range 

The petition does not address this 

factor. The bald eagle occurs naturally 

throughout the contiguous 48 States, 

Alaska, Canada and Mexico (Buehler 

2000). As such, the Sonoran Desert 

population does not represent the only 

surviving natural occurrence of the 

taxon. 


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Significance Criteria 4. The Discrete 

Population Segment Differs Markedly 

From Other Populations of the Species 

in its Genetic Characteristics 

Information Provided in the Petition 

The petition contends that review of 

all information regarding genetic 

analysis of the Southwestern desert 

nesting bald eagle reveals consistent 

uncertainty and the current 

understanding of genetics does not 

refute the discrete and isolated nature of 

the desert nesting bald eagle (CBD 

2004e; Hunt et al. 1992; SWCBD 1999). 

The petition specifically quotes excerpts 

from Hunt et al. (1992), which discuss 

genetics study methods, results, and 

conclusions. 

Response to the Petition 

We have addressed the genetic 

evidence provided by the petitioner in 

the analysis of discreteness above. 

Consistent with that analysis we have 

determined that the best available 

genetic information is inconclusive with 

regard to significance. We conclude that 

the petition does not present substantial 

information that the population differs 

markedly from other populations of the 

species in its genetic characteristics. 

Further, the petition does not present 

nor are we aware of any other factors 

that would lead us to believe that the 

Sonoran Desert population of the bald 

eagle differs markedly from the taxon as 

a whole. 

Conclusion 

We have reviewed the information 

presented in the petition, and have 

evaluated the information in accordance 

with 50 CFR 424.14(b). On the basis of 

our review, we find that the petition 

does not present substantial scientific or 

commercial information to indicate that 

the Sonoran Desert bald eagle 

constitutes a valid DPS. Although the 

population is discrete, the petition does 

not present substantial scientific 

information that the Sonoran Desert 

bald eagle may be significant in relation 

to the remainder of the taxon. Therefore, 

we conclude that the Sonoran Desert 

population is not a listable entity 

pursuant to section 3(15) of the Act. 

However, recognizing the volume of 

information provided in the petition, 

and the national importance of the bald 

eagle, we have also conducted a threats 

analysis. 

Threats Analysis 

Pursuant to section 4 of the Act, we 

may list a species, subspecies, or DPS of 

vertebrate taxa on the basis of any of the 

following five factors: (A) Present or 

threatened destruction, modification, or 

curtailment of habitat or range; (B) 

overutilization for commercial, 

recreational, scientific, or educational 

purposes; (C) disease or predation; (D) 

inadequacy of existing regulatory 

mechanisms; or (E) other natural or 

manmade factors affecting its continued 

existence. The Act identifies the five 

factors to be considered, either singly or 

in combination, to determine whether a 

species may be threatened or 

endangered. Our evaluation of these 

threats in terms of the petitioned action 

to reclassify the Sonoran Desert bald 

eagle from threatened to endangered, 

based on information provided in the 

petition and available in our files, is 

presented below. Throughout this 

finding we refer to the Sonoran Desert 

population of the bald eagle, because 

that is the petitioned entity; however, as 

noted above, this reference does not 

imply that we have determined, under 

to our DPS policy, that this population 

is a listable entity. Furthermore, 

although we have proposed the bald 

eagle in the lower 48 States for delisting 

(71 FR 8238, February 16, 2006), our 

petition finding does not address the 

proposed delisting or conditions that 

may occur if the delisting is finalized. 

A. Present or Threatened Destruction, 

Modification, or Curtailment of the 

Species’ Habitat or Range 

Development, Recreation, and Water 

Use 

The petition notes that the Southwest 

has already lost more than 90 percent of 

its historical riparian communities 

(AGFD 1993; Krueper 1993; Lofgren et 

al. 1990), and that the loss of riparian 

communities is continuing due to 

increasing development, dewatering via 

groundwater pumping and diversions, 

destructive cattle grazing, and lack of 

vegetation-rejuvenating floods. The 

petition contends that the Sonoran 

Desert bald eagle population faces 

imminent and accelerating loss of 

increasing amounts of habitat vital to its 

long-term survival. Specifically, the 

petition notes that most of the BAs are 

located along the Salt and Verde rivers 

near the Phoenix metropolitan area and 

the towns of Cottonwood and Camp 

Verde in Yavapai County, where habitat 

loss is occurring due to the increasing 

human population in central Arizona. 

The petition notes that the human 

population in Maricopa County is 

expected to double to more than six 

million people over the next 30 years 

(Arizona Republic 1998). Growth in 

Cottonwood, on the Verde River, is 

projected to increase by 148 percent and 

in Camp Verde by 158 percent between 

1994 and 2040 (Arizona Department of 

Economic Security 1994). The petition 

notes that increases in human 

populations of this magnitude will 

result in increased housing 

development, water demands, and 

recreational use. 

The petitioners contend that 

development will affect the suitability 

of many BAs due to their proximity to 

areas with large human populations and 

projected population growth rates. The 

petition notes that increased 

recreational use, development, and 

water use will follow increasing 

population sizes, and cites examples of 

past consultations, conducted by the 

Service under section 7 of the Act, 

addressing these issues. 

The petition cites recent examples of 

recreational impacts to Sonoran Desert 

bald eagle BAs, including river tubing 

on the Salt River, which increases the 

human presence near the Blue Point BA, 

as well as campground development at 

Roosevelt Lake, which could affect the 

Sheep and Tonto BAs. The petition 

cites, as development examples, a 360- 

home development and golf course 

within 1.0 mile (1.6 kilometers (km)) of 

the Box Bar BA; the development of 

lakeside resorts at Lake Pleasant near 

the Pleasant BA; and continued 

housing, road, and business 

developments along lower Tonto Creek 

near the Sheep and Tonto BAs (AGFD 

1999a, 2000). 

The petition notes that dewatering of 

the middle portion of the Verde River is 

accelerating so that flows have at times 

been reduced to 12 cubic feet per 

second (0.3 cubic meters per second) in 

summer months near the Camp Verde 

White Bridge gauge (Verde Natural 

Resources Conservation District 1999). 

The petition contends that this 

dewatering is resulting in a reduction in 

base flows, and increased populations 

in Cottonwood and Camp Verde are 

leading to increased groundwater 

pumping. The petition indicates that 

groundwater pumping in Arizona has 

repeatedly been demonstrated to result 

in a depletion of surface flows, 

degradation and loss of riparian 

communities, and adverse impacts and 

local extirpation of aquatic flora and 

fauna (ADWR 1994; Ewing et al. 1994; 

Glennon 1995; Glennon and Maddock 

1994; Hendrickson and Minckley 1984; 

McGavock 1996, Miller 1961; OwenJoyce and bell 1983, Stromberg 1993; 

Tellman et al. 1997). 

The petition notes that increased 

water demand is expected to have 

adverse effects on flows within rivers 

and resulting impacts on riparian 

communities. The petition further notes 

that 59.5 percent of all known desert 

bald eagle nests in Arizona have been in 


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riparian trees and snags (Driscoll 1999; 

E. Gardner, AGFD, pers. comm. 2006). 

The petition notes that bald eagles at 11 

BAs, including the Box Bar, Coolidge, 

Doka, Fort McDowell, Perkinsville, 

Pinto, 76, Sheep, Sycamore, Tonto, and 

Winkelman BAs, nest solely in riparian 

trees, and that the cottonwood trees 

used for nesting in these BAs have 

become overmature, are dying, and are 

not being replaced (AGFD 1991a, 2000). 

The petition contends that the loss of 

habitat in these BAs is particularly 

damaging to the future stability of the 

Sonoran Desert bald eagle population, 

as they have collectively contributed 22 

percent of all recorded fledglings since 

1971. The petition notes that the Fort 

McDowell BA has fledged 34 young, 

second only to the Blue Point BA, 

which has fledged 35 young (AGFD 

1999a, 2000). 

Substantial detail is provided in the 

petition regarding specific development 

activities and resulting effects to 

Sonoran Desert bald eagle BAs. The 

petition notes that pressures associated 

with human population growth are 

increasing and will continue to do so as 

the human population increases. 

Response to the Petition 

The information provided by the 

petitioner indicating that human 

population growth is expected to 

continue in areas in close proximity to 

or used by the Sonoran Desert bald eagle 

population appears accurate and 

reliable. Human population growth is an 

ongoing concern, and many of the bald 

eagle BAs in the Sonoran Desert 

population are within close proximity to 

this anticipated growth, including the 

Granite Reef, Orme, Rodeo, Sycamore, 

Doka, Fort McDowell, Box Bar, Needle 

Rock, and Bartlett BAs on the Verde 

River, and the Bull Dog, Blue Point, and 

Horse Mesa BAs on the Salt River, as 

well as the Pleasant BA at Lake 

Pleasant. As noted in the petition, 

recreation, development, and water use 

activities are ongoing and have 

increased since the bald eagle was 

listed. We have consulted on many of 

these actions through section 7 of the 

Act (including USFWS 1990b, 1996b, 

1997b, 1998, 2001a and 2003b on water 

developments and USFWS 1993a for 

recreation, as cited in the petition). In 

addition, the AGFD’s Projects 

Evaluation Program is available for 

Federal agencies or companies with a 

Federal nexus. This program can be 

used to evaluate the impacts of planned 

or future projects in areas where there 

may be a species of concern. The AGFD 

believes the program will help to ensure 

bald eagles and their habitat are 

considered and evaluated for possible 

effects from development projects 

(AGFD 2006, p. 14). 

Under section 7 of the Act, we have 

concluded to date that these actions 

would not jeopardize the continued 

existence of the bald eagle. The AGFD 

(2006c, p. 13) acknowledges that the 

need to accommodate human 

populations in proximity to a major 

metropolitan area like Phoenix will 

require ongoing management. However, 

they conclude that the species can be 

managed even under this scenario 

through the ‘‘awareness, collaboration, 

flexibility, planning, and willingness of 

all wildlife, land, and recreation 

managers (AGFD 2006, p. 13).’’

We work cooperatively with the 

AGFD and Federal land managers to 

minimize the potential threats to bald 

eagle BAs in close proximity to the 

major human population growth areas 

in Arizona by establishing BA closures 

and monitoring the sites. In 2006, the 

Bartlett, Box Bar, Granite Reef, Orme, 

and Tonto BAs were monitored through 

the Arizona Bald Eagle Nestwatch 

Program. The program not only interacts 

with members of the public to provide 

education, but can intervene if 

individuals approach the nests too 

closely. Similarly, the Southwest Bald 

Eagle Management Committee, 

composed of State, Tribal, Federal, 

private, and military agencies, meets 

twice each year to address ongoing and 

new threats, funding for needed efforts, 

and general issues affecting the bald 

eagle. 

With the exception of the Pleasant 

and Bull Dog BAs, all of the BAs in 

close proximity to Phoenix successfully 

fledged young in 2006. One bird from 

the Bull Dog BA was successfully 

fledged following fostering in the 

Granite Reef BA. Orme, Rodeo, Doka, 

Fort McDowell, Box Bar, Blue Point, 

and Horse Mesa fledged one young 

each, while Sycamore, Needle Rock, and 

Bartlett produced two young each. 

Additionally, many of these BAs have 

successfully produced young for many 

years and, while nest failures do occur, 

their overall productivity remains high. 

For example, the Bartlett BA has fledged 

28 young in 20 separate years between 

1971 and 2002; the Blue Point BA has 

fledged 38 young in 18 separate years 

between 1971 and 2002; and the Fort 

McDowell BA has fledged 41 young in 

23 years between 1971 and 2002 (AGFD 

2006, Table 7, pp. 48–50). 

The petitioners presented reliable and 

accurate data on the use of riparian 

areas for bald eagles, and on the 

potential loss of nest trees. In the 11 

BAs referenced by the petitioners, 

existing trees have become over-mature, 

are dying, and are not being replaced 

(AGFD 2006, p. 12). The eagles in the 

Doka, Fort McDowell, Granite Reef, 

Rodeo, 76, and Sheep BAs currently 

nest in overmature live trees or snags 

with few available replacements. Trees 

may be lost to floodwaters, as at Fort 

McDowell in 1995 and 2005, or 

inundated due to reservoir level 

increases, as at the Pinto and Tonto BAs 

at Roosevelt Lake. In some cases, 

alternate trees are not available, as is the 

case at the Pinto BA. Housing 

communities and water-table reductions 

limit the available trees at the Tonto BA 

(AGFD 2006, p. 13). 

The AGFD (2006, p. 13) notes that the 

Fort McDowell Yavapai Nation (FMYN) 

and Salt River Pima Maricopa Indian 

Community (SRPMIC) have submitted 

proposals to the Arizona Water 

Protection Fund and Wetlands 

Protection Fund to plant riparian trees. 

The U.S. Bureau of Reclamation is 

analyzing ground-water levels in the 

Pinto BA for possible cottonwood pole 

plantings, and has helped to implement 

riparian restoration strategies within the 

Tonto Creek Riparian Unit. Salt River 

Project has purchased property for 

riparian enhancements on Roosevelt 

Lake. The exact impacts of increased 

human population growth and riparian 

losses, as well as the success of planting 

efforts in riparian areas, are speculative 

at this point. Through these 

management efforts, however, managing 

agencies can begin to minimize the 

factors impairing riparian regeneration. 

We agree with the petitioner that 

human population growth, particularly 

in Maricopa and Yavapai counties, will 

continue. While we can anticipate the 

types of impacts that might occur, the 

exact results of those impacts on 

occupancy and productivity are 

speculative at this point. We remain 

concerned for BAs such as Bartlett, Blue 

Point, and Fort McDowell, which have 

contributed much to the productivity of 

bald eagles in the Southwest. However, 

we find that productivity remains high 

despite the ongoing nature of this threat. 

While this is an ongoing threat, bald 

eagles have continued to survive and 

reproduce, as evidenced by the 

increased number of BAs throughout 

Arizona, and as evidenced by the 

productivity of the BAs outlined above. 

We therefore find that the petitioners 

did not provide substantial information 

to lead us to conclude that this threat 

has increased the likelihood of 

extinction for the Sonoran Desert bald 

eagle population. 


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B. Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes 

No specific threats were identified in 

the petition for this category. 

C. Disease or Predation 

No specific threats were identified in 

the petition for this category. 

D. Inadequacy of Existing Regulatory 

Mechanisms 

Management 

The petition states that the Sonoran 

Desert population’s survival is 

dependent, in good part, on heroic 

human support and management by the 

Arizona Bald Eagle Nestwatch Program 

(ABENWP). The petition notes that, over 

a 2-year period in 1996 and 1997, 

13,999 human activities and 4,000 

gunshots were recorded within 0.5 mile 

(0.8 km) of 13 nests. The petition 

contends that signs, education, and the 

threat of fines are insufficient deterrents 

to people, and that monitoring by 

nestwatchers has been, and continues to 

be, a crucial component of Sonoran 

Desert bald eagle management (AGFD 

1999a, 2000). 

The petition additionally notes that, 

since 1983, 16 percent of all Sonoran 

Desert bald eagle fledglings have been 

saved by direct intervention of the 

ABENWP, with that intervention 

directly responsible for saving up to 60 

percent of a single year’s nestlings in 

some cases (USFWS 1992b). The 

petition notes that BAs such as Bartlett, 

Cliff, and 76 would rarely produce 

young without the aid of nestwatchers 

(Hunt et al. 1992). 

The petition further notes that the 

ABENWP could become inadequate in 

the future as its funding is not secure. 

The funding comes from State grants 

such as AGFD’s Heritage Fund, Federal 

agency contributions as mitigation for 

takings of the bald eagle under the Act, 

and volunteer funding. The petition 

finds that Heritage funding is insecure 

because it is derived from the State 

lottery, and income from the lottery has 

been decreasing. Additionally, the 

petition notes that there have been 

legislative attempts to divert lottery 

funds from protective wildlife activities. 

The petition contends that the proposed 

removal of the bald eagle from the 

Federal List of Endangered and 

Threatened Wildlife list will terminate 

mandatory Federal agency funding as 

well; the petition provides an example 

where the Bureau of Reclamation has 

asked us for clarification on terminating 

funding for one of its projects (USFWS 

1996c). The petition provides additional 

examples of the tenuous nature of 

funding for the ABENWP (AGFD 1994a; 

Arizona Republic 2003a, 2004c, 2004f) 

and states that there are few binding 

consultations for any agency to commit 

funding to existing bald eagle programs; 

funding assistance by agencies is 

primarily based upon available funds 

and where the agencies choose to 

allocate them. The petition notes that 

approximately 63 percent of all funds 

spent on bald eagles comes from 

agencies other than AGFD. 

Response to Petition 

Information in our files indicates that 

funding for the ABENWP comes from a 

variety of sources, including State 

Wildlife Grants, donations, AGFD 

Heritage Funds (State lottery), and 

matching funds for Federal grants. The 

petitioner’s contention that funding for 

the program will be significantly 

reduced or discontinued in the future is 

speculative. 

With regard to management and 

existing regulatory mechanisms, we 

evaluated whether a difference exists 

between the regulatory mechanisms 

currently protecting the bald eagle in 

the lower 48 States of the United States 

(inclusive of Sonoran Desert bald eagles) 

as a threatened species and the 

regulatory mechanisms protecting an 

endangered species (i.e., the petitioned 

action). As a threatened species with no 

special rule under section 4(d) of the 

Act, the bald eagle in the lower 48 

States of the United States (inclusive of 

Sonoran Desert bald eagles) is provided 

protection equal to that of an 

endangered species under the Act, 

except for penalties for illegal take. The 

prohibitions of the Act make it illegal 

for any person subject to the jurisdiction 

of the United States to take (includes 

harass, harm, pursue, hunt, shoot, 

wound, kill, trap, or collect, or to 

attempt any of these), import or export, 

ship in interstate commerce in the 

course of commercial activity, or sell or 

offer for sale in interstate or foreign 

commerce any listed species. It is also 

illegal to possess, sell, deliver, carry, 

transport, or ship any such wildlife that 

has been taken illegally. 

Further, the Service proposed to 

remove the bald eagle in the lower 48 

States from the List of Endangered and 

Threatened Wildlife on July 6, 1999 (64 

FR 36454) and reopened the comment 

period on that proposal on February 16, 

2006 (71 FR 8238). The comment period 

was extended on May 16, 2006 (71 FR 

28293). If this delisting action were to 

be finalized, we believe other existing 

regulatory protections afforded the 

Sonoran Desert bald eagle will provide 

adequate regulatory protection to this 

population. Our determination is based 

on the analysis with our delisting 

proposal and the fact that the existing 

regulatory protections are national in 

scope and not specific to the population 

level of a species. With regard to these 

existing regulatory protections, please 

reference the February 16, 2006 notice 

(71 FR 8238), reopening the comment 

period on the proposed rule to delist the 

bald eagle in the lower 48 States. In this 

notice, we provide an in-depth 

discussion of the protections afforded 

the bald eagle (including the Sonoran 

Desert bald eagle) by other Federal 

wildlife laws, including the Bald and 

Golden Eagle Protection Act (BGEPA) 

(16 U.S.C. 688–668d) and the Migratory 

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

712). In summary, the BGEPA prohibits 

taking, or possession of and commerce 

in, bald and golden eagles, with limited 

exceptions. Take under the BGEPA is 

defined as ‘‘to pursue, shoot, shoot at, 

poison, wound, kill, capture, trap, 

collect, molest or disturb’’ (16 U.S.C. 

668c). The MBTA implements various 

treaties and conventions between the 

United States and other countries and, 

unless permitted by regulations, it 

provides that it is unlawful to pursue; 

hunt; take; capture; kill; possess; offer to 

sell, barter, purchase, deliver; or cause 

to be shipped, exported, imported, 

transported, carried, or received any 

migratory bird, part, nest, egg or 

product, manufactured or not. 

Based on information provided by the 

petitioner and noted above, we find that 

no measurable difference exists between 

the regulatory protections provided the 

Sonoran Desert bald eagle in its current 

status as threatened than if it were 

assigned an endangered status (i.e., the 

petitioned action). Furthermore, we 

believe that other existing Federal 

wildlife laws will continue to provide 

adequate regulatory protections to the 

Sonoran Desert bald eagle if the bald 

eagle is delisted. Thus, we find the 

petitioner did not provide substantial 

information to lead us to believe that 

existing regulatory mechanisms may be 

inadequate to protect the Sonoran 

Desert bald eagle. 

Habitual Violation of Law and Lack of 

Agency Resolve 

The petition states that the Service 

has been engaged in efforts to downlist 

the bald eagle since at least 1989. The 

petition notes an attitudinal change 

accompanying downlisting efforts, and 

that this change contributes to 

increasing threats to the continued 

existence of the Sonoran Desert bald 

eagle. Specifically, the petition contends 

that the attitudinal shift perpetuates: (a) 

Cattle grazing within riparian habitat 

critical to Sonoran Desert bald eagles; 


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(b) dam operations with water releases 

that are improperly timed for 

replenishment of riparian nest trees; (c) 

dewatering of remnant, free-flowing 

rivers; (d) introduction of exotic fishes 

in native fish habitat; (e) continuing and 

increasing low-flying aircraft; and (f) 

approval of excessive amounts of take of 

Sonoran Desert bald eagles. The petition 

provides detailed information for each 

of these categories, which is 

summarized below. 

(a) Cattle Grazing Within Riparian 

Communities—The petition notes that 

cattle grazing in riparian areas is known 

to impede growth of replacement 

cottonwood nest trees (AGFD 1999a, 

2000). The petition cites numerous 

biological opinions by the Service as 

stating that riparian community loss is 

due, in part, to livestock grazing; that 

overgrazing continues as a threat and 

disturbance to bald eagles; and that 

overgrazing exacerbates adverse effects 

to riparian growth, as well as to existing 

eagle nesting, perching, and foraging 

habitat (USFWS 2001a, 2002a, 2002b, 

2003b). 

(b) Dam Operations Result in 

Improperly Timed Water Releases—The 

petition notes that poorly timed water 

releases are a threat to riparian 

communities (Stromberg et al. 1991). 

The petition further notes that loss of 

riparian communities continues on the 

lower Verde and Salt Rivers as a result 

of dam operations, and that 

maintenance of existing water 

development features, such as dams or 

diversion structures, is a continuing 

threat and disturbance to bald eagles 

(USFWS 2001a, 2003b). The petition 

contends that dam operations degrade 

existing eagle tree nesting and perching 

habitat and retard riparian regeneration; 

alter the hydrological regime of the 

lower Verde River by reducing the 

magnitude, frequency, and duration of 

high flow events; and restrict the flow 

of sediment, decreasing recruitment of 

early successional riparian species. The 

petition indicates that the effects of 

dams and their operation are the most 

important limiting factors in shaping the 

riparian plant community (Beauchamp 

2002). 

(c) Dewatering of Remnant, Freeflowing Rivers—The petition notes that 

flows in the Verde River have decreased 

to as low as 12 cubic feet per second 

(cfs) (3 cubic meters/second) during the 

month of June in some years (Verde 

Natural Resources Conservation District 

1999). The petition also notes that 

increasing groundwater pumping by the 

growing human population of 

Cottonwood and Camp Verde, which 

threatens to render sections of the Verde 

River intermittent (USFWS 1998). The 

petition further notes that the Arizona 

Department of Water Resources (ADWR) 

found that the Verde River baseflow is 

provided by groundwater discharge 

from the alluvium and Verde Formation, 

so any withdrawal from this aquifer is 

expected to eventually deplete Verde 

River flows (ADWR 1994). The petition 

again notes that the human population 

in Cottonwood and Camp Verde is 

expected to grow by 148 and 158 

percent, respectively, between 1994 and 

2040 (ADES 1994). The petition also 

notes that Prescott and Prescott Valley 

are developing a plan to use water from 

the Big Chino Basin, which may affect 

groundwater discharge into the upper 

Verde River (Arizona Republic 2000, 

2001). 

(d) Exotic Fish Introductions—The 

petition notes one study that found 

native fish populations to be a crucial 

component to suitable breeding habitat 

(Hunt et al. 1992). The petition 

indicates that at least 50 species of 

nonnative fish have been introduced 

into the Gila River basin (USFWS 

2001a), with potentially another 10 to 

15 incidental occurrences of other 

nonnative species. They note that 

nonnative species are considered to be 

extremely difficult, if not impossible, to 

remove once established (Aquatic 

Nuisance Species Task Force 1994). 

They also note that, in order to manage 

for native species, fish barriers are 

planned in areas like the upper Verde 

River, and that construction and 

maintenance of those barriers may result 

in take of bald eagles through 

harassment or harm due to the use of 

mechanized equipment, dredging of 

river channels to remove excess 

sediment, completion of required 

repairs, and added human activity to the 

area. A discussion under Factor E below 

indicates the petition’s concern on the 

decline of native species, especially 

Sonora sucker and desert sucker and 

their use by bald eagles as prey. 

(e) Continued and Increasing Low 

Flying Aircraft—The petition notes that 

there have been increases in low-flying 

aircraft, including private, military, and 

emergency aircraft, and that these 

aircraft are a concern for BAs on the 

lower Salt and Verde Rivers and for 

those BAs under military training routes 

(AGFD 1999a, 2000). The petition cites 

examples of aircraft recorded less than 

150 feet (45.7 meters) over active nests. 

The noise disturbance and sonic booms 

produced by military aircraft can flush 

incubating adults from the nest. The 

petition notes that the AGFD has 

worked with the Federal Aviation 

Administration and the Arizona 

Department of Transportation to 

establish a 2,000-feet (610-meters) above 

ground-level advisory along the Salt and 

Verde Rivers, but although marked on 

Arizona aeronautical maps, this 

advisory is generally disregarded. 

The petition notes that a biological 

opinion evaluated the Department of the 

Air Force proposal to widen and/or 

realign segments of military training 

routes in Arizona in 1994 (USFWS 

1994c). According to the petition, the 

Service acknowledged the loss of 9 

eagles or eggs and 18 disturbances per 

breeding season each year over the 50- 

year life of the project. Disturbances in 

the biological opinion are defined as 

aircraft use that results in the 

interruption of breeding or foraging 

activities, including the flushing or 

displacing of eagles engaged in breeding 

or foraging activities (USFWS 1994c). 

(f) Excessive Service Approval of 

Sonoran Desert Bald Eagle Deaths—The 

petition contends that the Service has 

approved Federal activities responsible 

for the deaths of at least 29 Sonoran 

Desert bald eagles in the last decade and 

claims that Federal activities reviewed 

by the Service through section 7 of the 

Act will result in a cumulative 491 

taking deaths over the next 50 years 

(USFWS 1992d, 1993a, 1994c, 1996b, 

1997b). 

Response to the Petition 

As required by section 7 of the Act, 

we have consulted on the potential 

impacts of cattle grazing, dam 

operations, dewatering of rivers, 

introduction of exotic fishes in native 

fish habitat, and low-flying aircraft to 

eagles and their habitat. Such analyses 

within biological opinions do not 

indicate a lack of agency resolve. It is 

our responsibility, under the Act, to 

enter into consultation with Federal 

action agencies when activities they 

authorize, fund, or carry out may affect 

a listed species or its critical habitat. 

During this process, we evaluate the 

impacts of the proposed project on 

listed species and determine how such 

impacts may be minimized and whether 

or not the project will jeopardize the 

continued existence of the species. If the 

project does not result in a jeopardy 

determination, we are responsible for 

working with action agencies to develop 

reasonable and prudent measures that 

will minimize the adverse impacts of 

the action on the species under 

consultation. Reasonable and prudent 

measures are restricted to actions that 

result in only minor changes to the 

proposed project and are within the 

legal authority and jurisdiction of the 

agency or applicant to carry out. 

The biological opinions cited within 

the petition analyze the impacts of 

various activities on the bald eagle and 


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its habitat, assess whether incidental 

take will occur, make a jeopardy/no 

jeopardy determination, and provide 

reasonable and prudent measures to 

minimize incidental take, when 

appropriate. In addition, each 

consultation includes sections on 

environmental baseline and cumulative 

effects, which are used to evaluate the 

effects of the current action against the 

background of previous impacts and 

total expected take for the species. For 

each of these opinions, we provided a 

take statement and determined that the 

level of take authorized would not 

jeopardize the continued existence of 

the species. These indicate that, 

although there may be some level of 

adverse effect resulting from the 

agency’s action, we do not believe the 

threats imposed by the various actions, 

when considered cumulatively with 

previous actions, were likely to 

jeopardize the continued existence of 

the species. 

We do not believe, based on the above 

discussion, we have authorized 

excessive levels of take for bald eagles 

in the Southwest. It is important to note 

that we believe the high level of take 

described in the petition with respect to 

the items E and F above is a 

misinterpretation on the part of the 

petitioners. The petition indicates that, 

for one consultation regarding 

expansion of military training routes, 

we allowed for the loss of 9 eagles or 

eggs and 18 nest disturbances annually 

over the 50-year life of the project. We 

provided a take statement for overhead 

flights that allows for take in the form 

of direct mortality of one adult or 

immature bald eagle, bald eagle 

nestling, or bald eagle egg, or two 

instances of disturbance per active nest 

per nest season. Incidental take in the 

form of mortality of more than one 

eagle, nestling, or egg would require the 

Air Force to reconsult immediately. 

Further, the reasonable and prudent 

measures require the Air Force to avoid 

active bald eagle BAs during the 

breeding season. The total take for this 

opinion was therefore 1 bald eagle 

mortality over the life of the project and 

18 disturbance events per year (2 at each 

of 9 BAs) outside of the breeding season 

each year for the life of the project. The 

total mortality associated with this 

particular project is therefore 1 bald 

eagle, rather than the 450 attributed to 

it in the petition (USFWS 1994, p. 13). 

With regard to existing protections 

afforded the bald eagle, we briefly 

discuss above the protections afforded 

the bald eagle under the Act (through 

listing as a threatened species and other 

Federal wildlife laws including the Bald 

and Golden Eagle Protection Act (BGEA) 

(16 U.S.C. 668–668d) and the Migratory 

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

712). We also explain why we believe 

these protections are adequate to protect 

the bald eagle and maintain recovered 

population levels. For a more in-depth 

discussion of these protections, please 

reference the February 16, 2006, notice 

reopening the comment period on the 

proposed rule to delist the bald eagle 

(71 FR 8238). 

We find that the petitioner did not 

provide substantial information to lead 

us to believe that existing regulatory 

mechanisms are inadequate to protect 

the Sonoran Desert bald eagle. We find 

that much of the information provided 

by the petitioner is speculative (e.g., 

reduced funding as a result of delisting) 

and not reliable (e.g., approval of 

excessive take). Additional information 

provided by the petitioner with regard 

to cattle grazing, dam operations, 

dewatering, introduction of exotic 

fishes, and low-flying aircraft does not 

establish a connection to the petitioned 

action, and does not indicate theses 

actions are occurring at a level that 

makes the Sonoran Desert bald eagle in 

danger of extinction (i.e., ‘‘endangered’’

as defined under the Act). As noted 

above in the Species Description, the 

numbers of occupied BAs in the 

Sonoran Desert population of bald 

eagles has continued to increase, 

reaching a total of 36 occupied BAs in 

2004. Productivity has remained 

relatively constant between 1987 and 

2005, at an annual average of 0.78 young 

per occupied BA for the Sonoran Desert 

population. This rate is within the range 

of many other states’ productivity rates 

(AGFD 2006, p. 5). 

E. Other Natural or Manmade Factors 

Affecting Its Continued Existence 

Small Population Size 

The petition notes that bald eagles 

once nested along every major river and 

large lake in the continental United 

States, and that they are no longer found 

in all areas of their historical range 

(Gerard and Bartolotti 1988). The 

petition further notes that the Sonoran 

Desert population of the bald eagle is 

extremely small and without prospect 

for significant expansion. The petition 

notes that there are fewer than 60 

nesting pairs of bald eagles in the 

population, and that the population 

occupying BAs may be overestimated. 

Their concern for overestimation of the 

population is based on the fact that 

members of breeding pairs recorded as 

occupying, but not breeding, in a BA 

may also occupy adjacent BAs. They 

note that two males were observed to 

move between BAs, and it is possible 

that adults recorded as occupying one 

BA may have come from an adjacent 

occupied BA. 

The petition notes that BAs may have 

been occupied in years prior to their 

discovery, and that, if this is the case, 

the continued increase in the number of 

BAs represents an increase in the 

number of discovered BAs, rather than 

an increase in the actual number of 

breeding birds. Undercounting of the 

population in previous years has 

resulted in a greater discrepancy 

between past and current known 

numbers of breeding birds, which 

reflects a greater increase in the 

population than that which might 

actually have occurred. 

The petition further notes that there is 

not enough surviving suitable habitat 

available to allow for the population to 

increase substantially or expand its 

distribution. They note that the AGFD 

has concluded that riparian community 

improvement and prey base 

modifications will be necessary before 

population sizes increase in Arizona 

(AGFD 1999, 2000). Thus, the 

petitioners believe that the Sonoran 

Desert population will likely continue 

to remain small into the foreseeable 

future. 

The petition notes that the small size 

of the Sonoran Desert bald eagle 

population is, in and of itself, 

problematic. Using AGFD survival 

estimates of juveniles and nestlings, the 

petitioners estimate that there are 

approximately 166 individual eagles in 

the Sonoran Desert population. The 

petition maintains that the population 

dynamics of such a population are 

essentially similar to those of an 

isolated metapopulation. The petition 

references a study examining the effects 

of widespread habitat destruction on 

regional metapopulations of raptors, and 

notes that the study found most species 

persist regionally as metapopulations or 

as sets of populations linked by 

dispersing individuals (Thomas et al. 

1990). This allows for recolonization of 

unoccupied habitat patches following 

local extinction events. However, the 

petition states that the loss of suitable 

habitat patches, or disturbances in the 

surrounding landscape, can disrupt this 

process and lead to the regional 

extinction of a species. The cited study 

indicates that the persistence of the 

raptor species is at risk in significant 

portions of its range due to continued 

destruction and concomitant 

fragmentation of its habitat. As this 

pattern continues, a previously 

continuous population is separated into 

smaller, isolated demographic units that 

are at higher risk of local extinction due 


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to demographic factors and/or 

environmental phenomena. 

The petition contends that four 

‘‘categories of analysis’’ are applicable 

to the question of the long-term 

survivability for raptors in general, 

including demographics, genetics, patch 

dynamics, and environmental change. 

The petition indicates that, based on 

population biology principles, if a 

typical vertebrate species such as a 

raptor is reduced to a genetically 

effective size of 50, it may suffer from 

inbreeding depression (Barrowclough 

and Coats 1985; Franklin 1980; Soule 

1980). Further, demographic 

stochasticity and inbreeding depression 

may interact, with the effects of one 

exacerbating the other, and hasten the 

decline of a population (Gilpin and 

Soule 1980). The petition states that 

populations that are reduced in size 

tend to lose genetic variability through 

genetic drift, reduced average individual 

heterozygosity, and a reduced pool of 

allelic variation. The petition contends 

that a population size of roughly 1,000 

or larger is required to maintain all of 

the genetic variation of that population 

(Soule 1986). Below that size, the 

population will lose genetic variation at 

a rate proportional to the size of the 

population. The petition concludes that 

the Sonoran Desert population has 

characteristics of extended adult 

longevity, high juvenile mortality, 

intense territoriality, and may be in a 

position to enter a geometric population 

decline (Lande 1987). 

Mortality 

The petition, which notes adult 

mortality is higher than recruitment for 

the population, contends that the level 

of mortality in the Sonoran Desert 

population is higher than can support a 

stable population. The petition states 

that, from 1987 to 1990, the rate of 

mortality for breeding-adults has 

averaged 16 percent of the breeding 

population per year or 5.25 breeding 

adult mortalities per year. From 1991 to 

1998, the rate of mortality was 11.9 

percent, or 5.13 breeding-adult 

mortalities per year (Beatty and Driscoll 

1996; AGFD 1999a, 2000). 

The petition further contends that the 

high presence of subadults in breeding 

pairs likely reflects high adult mortality 

rates. The petition notes that Hunt et al. 

(1992) indicated that the presence of 

subadults in breeding pairs may show 

that excessive adult mortality is 

draining the floating (i.e., non-breeding) 

segment of adult bald eagles. As a result, 

subadult eagles are recruited into the 

breeding population, either forming a 

new pair bond with another nonbreeding bird, or more frequently, 

replacing the mate of another breeding 

eagle. Twelve subadult-plumaged birds 

were observed holding territories in 

Arizona from 1987 to 1990, with seven 

subadult-plumaged birds observed 

holding territories in Arizona since 

1991. The petition notes that the AGFD 

(1994b) found that, for 39 known 

vacancies of BAs, 15 (38.5 percent) were 

filled by adults and 24 (61.5 percent) by 

near-adults or subadults. The petition 

states that this pattern is not observed 

in other populations (Gerrard et al. 

1992), and that in Saskatchewan, 

population stability was maintained in 

part by bald eagles deferring first 

breeding to age six. The petition states 

that a 1992 survey of 14 bald eagle 

biologists throughout North America 

determined that the known incidence of 

breeding subadults outside of Arizona 

was 0.02 percent (Hunt et al. 1992). The 

petition concludes that the persistent 

presence of three- and four-year-old 

breeding bald eagles in Arizona has 

created concern for the health of the 

breeding population. 

The petition contends that mortality 

for fledglings is also excessive, and that 

most Sonoran Desert nestlings die 

prematurely. The petition notes that, 

according to AGFD data, from 1987 to 

1998, 97 fledglings have been found 

dead (Hunt et al. 1992; Mesta et al. 

1992; Beatty and Driscoll 1996b; AGFD 

1991, 2000), and concludes that few 

Sonoran Desert bald eagles survive to 

adulthood. 

Productivity 

The petition states that the 

reproductive rates for the Sonoran 

Desert population are lower than those 

known for bald eagles in any other 

location. The petition indicates that the 

AGFD (1999a, 2000) determined that 

productivity rates are lower than those 

recorded throughout North America. For 

the Sonoran Desert population, 

productivity rates from 1975 to 1984 

were 0.92 young per occupied BA, but 

since then, the average productivity rate 

has been 0.78 young per occupied BA. 

The petition notes that productivity 

rates over a similar time span in Alaska, 

Florida, Washington, and Wisconsin 

averaged 0.96 young per occupied BA 

(Sprunt et al. 1973; McAllister et al. 

1986; Kozie and Anderson 1991). The 

petition adds that, in some areas of the 

Sonoran Desert population, productivity 

rates are even lower. For example, 

productivity along the Salt River 

declined to 0.26 young per occupied BA 

in the 1990s. 

The petition further contends that 

BAs that formerly produced the majority 

of the fledglings are producing fewer 

fledglings, and that the most productive 

nests are in relatively close proximity to 

the rapidly growing Phoenix 

metropolitan area, so that survivability 

in these BAs is becoming increasingly 

problematic. The petition states that the 

Salt and Verde Rivers support the bulk 

of the Sonoran Desert population, and 

that it is in the lower parts of these 

drainages and nearby lakes where prey 

is most abundant and bald eagles are 

most productive. However, the 

proximity of these areas to Phoenix 

results in high recreation use. Due to 

predicted human population expansion 

(see factor A above), the petition 

predicts increased recreational and 

development pressures in close 

proximity to BAs along the Salt and 

Verde Rivers (ADWR 1999a, 2000; 

Arizona Republic 2000, 2001; Chino 

Valley Review 2004; Prescott 2001; 

Prescott Daily Courier 2004a, 2004b; 

USFWS 2001a). 

The petition further notes that 

Sonoran Desert bald eagles on private 

lands are either not reproducing or are 

destined to fail. The petition cites the 

Winkelman BA as an example, noting 

that this BA on private property is now 

surrounded by housing, recreation, and 

industry. The petition states that the 

Camp Verde and Perkinsville BAs are 

also on private property, and are 

surrounded by private lands that have 

recently been sold or for which plans to 

sell are underway. The petition cites the 

reproductive history of these BAs, 

noting that the Camp Verde and 

Winkelman BAs have a record of 

reproductive failure, and that the 

Perkinsville BA failed in 2002 and faces 

further threats from potential 

dewatering of the upper Verde River. 

The petition includes information 

developed by the petitioners through 

the use of Vortex (version 9) software, 

which models wildlife population 

dynamics and evaluates many of the 

threats that may cause small 

populations to go extinct. The petition 

notes that the petitioners worked with 

AGFD data. Some of the model 

assumptions are that the population is 

a closed population and not 

demographically linked to other 

populations, and that there is a 1:1 ratio 

of males to females in the adult 

population. Because the petitioners 

determined that fecundity in the lower 

Verde and Salt BAs were inflated 

artificially by AGFD’s stocking of exotic 

rainbow trout and Salt River Project’s 

release of native fish captured from 

irrigation canals, BAs were divided into 

two groups: (1) Those on the lower Salt 

and Verde Rivers, and (2) those in other 

areas. 

Additional detail regarding 

parameters used in and determinations 


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derived from the model are in the 

petition. The petition notes that the 

model determined that juvenile and 

adult survival were the most critical 

parameters for the model. The petition 

indicates that the model demonstrates a 

high risk of extinction for the Sonoran 

Desert population within the next 57 to 

82 years. 

Response to the Petition 

The majority of the data and 

information presented in the petition is, 

in part, consistent with the information 

in our files. Our information indicates, 

however, that there are no data 

supporting the statement that nests on 

private property are destined to fail 

simply due to their location relative to 

private land. While it is true that the 

Winkelman BA has been abandoned, the 

Camp Verde nest may have failed due 

to flooding, which is unrelated to the 

land’s ownership. Moreover, two BAs 

on private land (Sheep and Beaver) are 

currently occupied and produced young 

in 2005 and 2006, respectively. 

In addition, we do not believe the 

population is overestimated due to 

individuals occupying more than one 

BA; this behavior has been observed at 

only two BAs, and the survey protocols 

and definition of occupancy currently in 

use limit this type of bias from 

occurring (E. Gardner, pers. comm. 

2006, p. 3). 

With respect to mortality, AGFD 

(2006c, p. 24) notes that adult mortality 

rates of 16 percent (from 1987 to 1990) 

and 12 percent (from 1991 to 1998) are 

higher than, but within the range of, 

other populations, which ranged from 5 

percent in Northern California to 17 

percent in Chesapeake Bay. Bald eagles 

in Maine experienced a nine-percent 

mortality rate, while those in Coastal 

Alaska were a 12-percent mortality rate. 

For nestling mortality, the petition 

concluded that few Sonoran Desert bald 

eagles survive to adulthood. Stalmaster 

(1987, p. 143) found that, of 433 

nestlings surveyed in the southwestern 

region, an average of 85 percent 

survived to fledging, resulting in a mean 

nestling morality rate of 15 percent. By 

comparison, Hunt et al. (1992, p. C–108) 

concluded that the nestling mortality 

rate for the Arizona population was 

approximately 0.9 percent higher, or at 

15.9 percent. Following Hunt’s study, 

from 1991 to 2006, nestling mortality 

was approximately 24 percent. While 

this represents an eight percent increase 

from data provided by Hunt et al. (1992, 

p. C–108), this may be due to increased 

monitoring effort through the ABENWP 

compared to earlier Arizona monitoring 

efforts and those efforts in other states. 

Daily monitoring through the ABENWP, 

monthly helicopter flights, and periodic 

on-the-ground visits throughout the year 

may have more accurately detected 

surviving fledglings and fledgling 

mortality than efforts that involved 

fewer follow-up visits. While we believe 

this nestling mortality rate warrants 

continued monitoring, a 76-percent 

survival rate does not indicate that most 

Sonoran Desert nestlings die 

prematurely, as contended by the 

petition. 

The information provided by AGFD 

(2006c) and Stalmaster (1987) indicate 

that mortality rates for bald eagles 

within the Sonoran breeding population 

are similar to those experienced in other 

populations in the United States, as are 

productivity rates. In addition, the 

population has continued to increase in 

terms of the number of breeding pairs 

and productivity, as noted above under 

the ‘‘Species Information.’’ Therefore, 

we find that the petitioner did not 

provide substantial information to 

indicate that the level of mortality and 

small population size may place the 

Sonoran Desert population of bald eagle 

in danger of becoming extinct. 

Declining Prey Base 

The petition notes that the primary 

prey item for bald eagles during spring 

is the native Arizona sucker population, 

consisting of desert and Sonora suckers. 

The petition cites recent reports 

indicating that Sonora sucker and desert 

sucker remain in approximately 73 

percent and 74 percent, respectively, of 

the locations in which they were 

historically recorded. These fish 

populations have a low probability of 

local extirpation, but fragmentation of 

their range and isolation of individual 

populations could further reduce their 

occurrence in a watershed (Desert 

Fishes Team 2004). With respect to the 

potential effects of a decline in the 

native fish prey base, the petition quotes 

the biological opinion completed for the 

Central Arizona Project (CAP) (USFWS 

2001a). The petition indicates that in 

the CAP opinion the Service concluded 

that take of bald eagles was anticipated 

to occur as harm, through alteration of 

the quantity and quality of the food 

base. 

The petition cites, as a specific 

example, the effects of the decline of 

native suckers on the Salt River. The 

petition states that native suckers, 

which are a crucial prey species during 

the breeding season for bald eagles, 

became absent from the Salt River 

during the 1990s. The petition cites 

studies that note that the lack of native 

fish species along those portions of the 

Salt River occupied by bald eagles may 

have reduced productivity from 0.69 

young per BA in the 1980s to 0.26 in the 

1990s (Hunt et al. 1992). 

Response to the Petition 

The petition presents reliable and 

accurate information to indicate that 

native fishes are continuing to decline 

and effects to the prey base can have 

effects on the Sonoran Desert 

population of bald eagles. As outlined 

below, the effects of a reduced prey base 

seem to be affecting productivity rather 

than occupancy. Occupancy of these 

BAs remains fairly constant through 

2002. Between discovery in 1978 and 

2002, the Cedar Basin BA was 

unoccupied for only 1 year (1980). The 

Canyon and Pinal BAs were unoccupied 

for 2 years each (2001 and 2002 for the 

Canyon BA, 1986 and 2001 for Pinal). 

The Cibecue BA was unoccupied for 3 

years (1974, 1976, and 1981). The Lone 

Pine and Redmond BAs have remained 

occupied since their discoveries in 1984 

and 1975, respectively (AGFD 2006, 

Table 7, pp. 48–50). Two BAs, Ash and 

Mule Hoof, are no longer considered 

occupied. The Ash BA was occupied in 

1984 and 1985, but has been 

unoccupied for 10 consecutive years, 

and is no longer included in the list of 

occupied BAs. Mule Hoof was 

sporadically occupied in the 1980s and 

the early 1990s, and was removed in 

2002 after 10 consecutive years of 

unoccupancy (AGFD 2006, Table 7, pp. 

48–50). 

However, while the upper Salt River 

BAs have remained largely occupied, 

productivity for the six BAs has 

remained low, declining after 1992 

although remaining somewhat constant. 

From 1992 to 2002, between 0 and 3 

total young have been produced each 

year (AGFD 2006, Table 7, pp. 48–50). 

Hunt et al. (1992, p. A–46) note that 

bald eagles in central Arizona forage on 

free-flowing and regulated rivers, 

reservoirs, small tributary streams, and 

on land, and that most, if not all pairs, 

use more than one of these 

environments during a given nesting 

season. Data indicate eagles commonly 

switch forage locations and/or prey 

species in response to changes in the 

distribution of prey and carrion. Hunt et 

al. (1992, p. A–46) cite as an example 

a study on a male eagle from the Blue 

Point BA that took a variety of prey on 

both reservoir and riverine habitats. 

While those BAs that rely primarily on 

riverine habitat for prey, such as those 

in the upper Salt River, are showing a 

reduction in productivity, overall 

productivity for bald eagles throughout 

Arizona and within the Sonoran Desert 

population has remained stable between 

1987 and 2005, and is comparable to 


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that in other portions of the species 

range. 

As the petitioners note, low 

productivity has been an issue on the 

upper Salt River since the 1980s. 

However, as noted above, the BAs in 

this area continue to remain occupied, 

and productivity, while low, remains 

fairly constant. Consequently, we do not 

perceive a new or increased threat due 

to a reduced prey base in this area. The 

situation on the upper Salt River is 

likely observed in other streams as well, 

where eagles rely primarily on rivers for 

foraging. This situation requires 

continued monitoring, and 

improvements need to be made in 

managing for native fishes, and 

increasing overall productivity in these 

BAs. However, there has been increased 

productivity in other BAs, including 

some of those that also rely on rivers for 

foraging. This increase is in part 

attributable to the increase in the total 

number of BAs throughout Arizona. 

Therefore we find that the petitioner did 

not provide substantial information to 

indicate that threats from reductions in 

prey base are occurring at a level that 

leads us to conclude that the petitioned 

action may be warranted. 

Contaminants 

The petition claims that insecticides, 

such as carbofuran, endosulfan, 

fenthion, phorate, and terbufos 

(American Bird Conservancy 2004a, 

2004b; Center for Biological Diversity 

2004c; EPA 2004c, 2004d, 2004e, 2004f; 

University of Arizona 2004; USDA 2001; 

USFWS 1995), continue to threaten the 

bald eagle, noting that hundreds of bald 

eagle deaths have been linked to 

carbofuran nationwide (American Bird 

Conservancy 2004b). The petition 

further states that DDT and its 

derivatives are still found in Arizona 

waterways, and states that toxic levels 

of DDE (a breakdown product of DDT) 

were found in an addled egg from the 

Sycamore BA in 1997 (AGFD 1999a, 

2000; USGS 2004). 

The petition notes that chlorfenapyr 

resulted in a decline in the number of 

eggs, viable embryos, and hatchlings of 

mallards, and that this chemical has 

been put to use within the United States 

(EPA 1999). The petition further states 

that toxic levels of mercury have been 

found in eggs from the Verde and Salt 

River BAs, and that mercury 

contamination has also been found in 

the Tonto Creek BA and Gila River at 

levels high enough to cause failure in 

eggs (AGFD 1999a, 2000). The petition 

notes that mercury concentrations in the 

Sonoran Desert population were higher 

than those reported for most other North 

American populations (Grubb et al. 

1990). The petition states that studies 

have determined that concentrations of 

mercury above 2 parts per million (ppm) 

are known to impair hatching (Newton 

1979), and concentrations of 1.5 to 4.5 

ppm are considered toxic (Ohlendorf 

1993). The petition notes tha seven eggs 

from the Tower, 76, Pinal, and 

Winkelman BAs have toxic levels of 

mercury ranging from 2.11 to 8.02 ppm, 

and that elevated levels of mercury 

between 1.5 and 2.0 ppm were found in 

three eggs from the Tower and 

Horseshoe BAs (AGFD 1999a, 2000). 

The petitioners note that the Service 

considered concentrations of heavy 

metals to be a concern in Arizona 

(USFWS 2001d). 

The petition contends that mercury in 

bald eagles comes primarily from their 

prey, noting that contaminants studies 

detected elevated levels of mercury in 

prey items ranging from 0.06 to 0.97 

micrograms per gram (μ/g) with the 

highest mean levels recovered from 

Lake Pleasant, the Salt River, and Alamo 

Lake (King et al. 1991). The petition 

contends that these highest means were 

above the National Contaminant 

Biomonitoring Program’s 

recommendation for no observable 

effects of 0.1 μ/g (Eisler 1987). 

The petition notes that 

methylmercury is the form of mercury 

that accumulates at greater rates than 

inorganic mercury, and that most 

mercury in fish or wildlife organisms is 

in the form of methylmercury (Bloom 

1989). The petitioners further note that 

methylmercury is more efficiently 

absorbed (Scheuhammer 1987) and 

preferentially retained (Weiner 1995). 

The effects of mercury contamination 

have been studied in mallards. The 

petition cites a study on the effects of 

mallards that were fed 3.0 ppm 

methylmercury dicyandiamide for 2 

years. In these mallards lesions resulted, 

including necrosis and hemorrhaging in 

the lining of the brain (Heinz and Locke 

1975). The petition contends that the 

risk to bald eagles is increasing, as eggs 

collected between 1982 and 1984 had 

concentrations of approximately 0.39–

1.26 ppm (K. King, pers. comm.), while 

those collected between 1994 and 1997 

had concentrations ranging from 2.11 to 

8.02 ppm (Beatty et al. unpub. data), up 

to six times higher than those collected 

between 1982 and 1984. 

Response to the Petition 

The petition provides information 

specific to bald eagles in Arizona to 

indicate that contaminants (in the form 

of DDT and related breakdown 

products, and mercury) continue to 

present a potential threat to the Sonoran 

Desert bald eagle population. We find 

that some of the information presented 

by the petitioner is in error. With 

respect to carbofuran, it is important to 

that note the granular form that caused 

the extreme risks in grain-eating birds is 

not registered for use in Arizona 

(Extoxnet 2006, p. 1). Similarly, 

chlorfenapyr is not registered for use in 

Arizona (EPA 2006, p.1). 

The discussion on mercury indicates 

that mercury levels were found to 

exceed 2 ppm for 13 eggs collected 

between 1994 and 1997. AGFD (2006, p. 

21) notes that, from 1994 to 2004, 27 

addled bald eagle eggs in Arizona 

showed mercury levels ranging from 

0.55 to 8.02 ppm. The AGFD (2006, p. 

21) classifies 10 of these eggs as toxic, 

exceeding 2.0 ppm; 11 eggs as having 

elevated levels of mercury (1.5 to 2.0 

ppm), and four eggs as having lesser 

concentrations (1.0 to 1.5 ppm). The 10 

eggs classified as toxic came from the 

Box Bar, Needle Rock, Pinal, 76, Tower, 

and Winkelman BAs. While eggs tested 

for mercury were addled and did not 

produce young, successful production 

of young has occurred at these BAs 

following the year or years in which 

mercury was detected (viable eggs are 

not collected and tested for mercury). 

For example, with toxic mercury levels 

in 2003, the Box Bar BA successfully 

produced young in 2004 and 2005. 

Following toxic mercury level detection 

in 2003, the Needle Rock BA 

successfully produced young in 2004. 

Following toxic mercury levels in 1995, 

the Pinal BA successfully produced 

young in 2000, 2002, 2004, and 2005. 

The 76 BA, which had the highest ever 

recorded mercury level for eggs from 

Arizona in 1995, successfully produced 

young in 1996, 1997, 1998, 1999, 2000, 

and 2001. Following toxic mercury level 

detection in 1994 and 1995, the Tower 

BA successfully produced young in 

1996, 1997, 1998, 1999, 2000, 2002, 

2003, and 2005. No information is 

available for the Winkelman BA, which 

has been unoccupied since 1999. These 

data indicate that mercury in eggs at a 

given nest site may cause nest failure for 

one season, but does not prevent future 

production of young. 

DDE does continue to be detected in 

eggs, with the recent measurement of 

4.23 ppm wet weight in one egg from 

the Rodeo BA in 2002. Weimeyer et al. 

(1984, p. 541) found that reductions in 

productivity occurred when DDE values 

in bald eagle eggs were between 3 and 

5 ppm (wet weight). This level has been 

reached at the Tonto, Tower, Sycamore, 

and Rodeo BAs. The most complete 

DDE data set over time is from the 

Tower BA, where DDE concentrations 

declined from 3.2 ppm in 1994, to 0.91 

ppm in 2001. The Tonto BA has 


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produced young since DDE levels of 

4.17 ppm wet weight were found in 

q2001. Following DDE levels of 3.20 

ppm wet weight, the Tower BA 

produced young in 1996 through 2003, 

2005, and 2006. At the Sycamore BA, 

DDE levels of 7.00 ppm wet weight were 

detected from an egg collected in 1997, 

but the BA produced young in 1998, 

1999, and 2001 through 2006. The 

Rodeo BA, with DDE levels of 4.23 ppm 

in 2002, produced young in 2004 and 

2006 (AGFD 2006, Table 4, p. 22; 2006 

unpubl. data). 

The information presented on the 

mercury levels found in eggs from the 

Verde and Salt River BAs is generally 

accurate, as is that for the Tonto Creek 

and Gila River area. The information on 

DDT and its breakdown products is also 

generally accurate. Productivity at those 

BAs affected by high levels of mercury 

and DDE indicates that, while nest 

failure may result when those levels are 

detected, young are produced in 

subsequent years. We have been 

evaluating the effects of mercury, DDE, 

and pesticides for many years, and we 

conclude that these effects should be 

monitored but are not likely to 

jeopardize the continued existence of 

the species. We do not believe that the 

petitioner provided substantial 

information to indicate contaminantrelated threats are present at a level that 

leads us to conclude that the petitioned 

action may be warranted. 

Fishing Line and Tackle 

The petition cites AGFD data that 

finds fishing line and tackle have been 

found in nests and have entangled bald 

eagles. There have been 62 separate 

instances involving entanglement, and 

19 BAs with fishing line and/or tackle 

in nests or entangled individuals since 

1986 (Hunt et al. 1992; Beatty 1992; 

Beatty and Driscoll 1994a; Beatty et al. 

1998). The petition notes that 

mortalities have resulted from 

entanglement. The petition indicates 

that bald eagles encounter fishing line 

primarily by catching dead or dying fish 

with fishing line or tackle still attached, 

but that some birds have become 

entangled while perched on the 

shoreline or while feeding on dead 

shorebirds and waterfowl that have 

themselves been entangled. 

The petition states that the persistent 

occurrence of fishing line indicates the 

level of recreational pressure in many of 

the BAs, and contends that as the 

human population of central Arizona 

increases, so will the accompanying 

recreational demands on riparian areas 

(AGFD 1999a, 2000). The petition 

concludes that these increased 

recreational pressures will lead to even 

greater incidences of fishing line and 

tackle in nests and resulting in adverse 

effects on Sonoran Desert bald eagles. 

Response to the Petition 

The petition does not mention 

AGFD’s monofilament recovery 

program. Although this program is 

voluntary, it has helped to educate 

anglers and reduce the amount of 

improperly disposed monofilament. For 

probable causes of mortality in bald 

eagles in Arizona between 1987 and 

2005, monofilament is listed as causing 

one adult mortality and two nesting 

mortalities. It is ranked as the fifteenth 

most common cause of mortality, and 

responsible for 3 out of 281 deaths, or 

approximately 1.1 percent (AGFD 2006, 

Table 6, p. 25). Monofilament is an 

ongoing problem for Sonoran Desert 

bald eagles, but represents a minor 

threat. In part, we attribute this to the 

active management of the ABENWP, 

which we anticipate will continue. 

Additionally, wildlife personnel 

entering nests to conduct annual 

banding are instrumental in removing 

large quantities of monofilament (AGFD 

2006, p. 11). We find the petitioner did 

not provide substantial information to 

indicate that monofilament 

entanglement may represent a threat 

that puts the Sonoran Desert bald eagle 

population in danger of extinction. 

Climate Change 

The petition notes that adaptation to 

the Southwest’s combination of high 

temperature and low humidity is 

considered one of the characteristics 

that demonstrate the uniqueness of the 

Sonoran Desert eagle population. The 

petition continues, however, to state 

that heat stress is also a leading cause 

of nestling mortalities. The petition 

notes that the Service (USFWS 1990b) 

determined that this situation will likely 

become more common, citing more days 

above 100 °Fahrenheit in 1990 than 

1989. The petitioners indicate that older 

nestlings have fallen from nest cliffs 

while attempting to reach shade or have 

fledged prematurely from nests without 

shade, which usually results in their 

mortality. The petition cites studies 

indicating that 23 nestlings died and 7 

pre-fledged due to heat stress (Hunt et 

al. 1992). The petition cites additional 

information regarding heat-related 

mortalities. 

In addition to heat, the petition notes 

that global warming will lead to more 

frequent drought cycles. The petitioners 

note the Service (USFWS 2003b) 

determined that, between 1993 and 

2001, eagles that depend on Roosevelt 

Lake for food had lower reproduction as 

the lake’s surface area declined. 

Response to the Petition 

The petition presents some 

information to indicate that heat is a 

stressor for the Sonoran Desert bald 

eagle, and that drought and declining 

water levels at reservoirs may result in 

decreased productivity. The AGFD 

notes that heat stress is the fourthleading cause of known nestling 

mortalities, behind predation, 

parasitism, and starvation (E. Gardner, 

AGFD, pers. comm. 2006). It is ranked 

as the sixth greatest threat to bald eagles 

in all age classes (AGFD 2006, Table 6, 

p. 25). 

Productivity for the Sonoran Desert 

population of bald eagles has reached its 

highest level yet for 2003 (at 0.62 young 

per occupied BA), 2004 (at 1.06 young 

per occupied BA), and 2005 (at 1.01 

young per occupied BA), while the 

Southwest experienced drought 

conditions. Climate variability and 

drought conditions may ultimately 

cause adverse effects to the bald eagle; 

however, the long-term effects of 

ongoing drought for desert-adapted 

birds like those of the Sonoran Desert 

bald eagle population are unknown. The 

bald eagle is successful in a wide range 

of climate conditions. We do not find 

that the petitioner provided substantial 

information to demonstrate that drought 

and increased heat will lead to adverse 

effects to the Sonoran Desert population 

of bald eagles that would cause them to 

be in danger of becoming extinct. 

Therefore, we find that the petitioner 

did not provide substantial information 

to indicate that climate-related threats 

are occurring at a level that leads us to 

conclude that the petitioned action may 

be warranted. 

Eggshell Thinning 

The petition notes that eggshell 

fragments from 32 Arizona bald eagle 

BAs were collected, measured, and 

averaged by nest from 1977 to 1997. 

These means were then compared with 

the 0.591 mm mean from Baja 

California, which is the closest known 

bald eagle population to Arizona with 

pre-DDT eggshell measurements. The 

petition cites Wiemeyer et al. (1984) in 

noting that eggshell thinning of greater 

than 10 percent causes problems in 

reproduction for other bald eagle 

populations. Similarly, the petition 

notes that studies have determined that 

a population would experience 

reproductive problems when eggshell 

thinning has become severe (15 to 20 

percent) for a period of years (Anderson 

and Hickey 1972). 

Mean eggshell thicknesses were 

compared with those from Baja 

California, which had a mean of 0.591 


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mm (0.024 in). The petition cites four 

studies on eggshell fragments for 

southwestern bald eagles (Grubb et al. 

1990; Hunt et al. 1992; Mesta et al. 

1992, Driscoll and Beatty, unpublished 

data). The results of these studies found 

eggshell thickness means of 0.539 mm 

(0.021 in) for 32 sets of eggshell 

fragments from 14 BAs between 1977 to 

1985; 0.562 mm (0.022 in) for 71 sets of 

eggshell fragments from 23 BAs between 

1987 and 1990; 0.552 mm (0.022 in) for 

27 sets of eggshell fragments from 18 

BAs between 1991 and 1992; and 0.534 

mm (0.021 in) for 135 sets of shell 

fragments collected from 27 BAs 

between 1993 and 1997. In comparison 

to the Baja California mean eggshell 

thicknesses, these studies found a 

comparative 8.8 percent thinning for 

1977 to 1985; 4.9 percent from 1987 to 

1990; 6.6 percent in 1991 and 1992; and 

9.7 percent from 1993 to 1997 (Grubb et 

al. 1990; Hunt et al. 1992; Mesta et al. 

1992, Driscoll and Beatty, unpublished 

data). The petition notes that, since 

1993, the annual percent thinning 

exceeded 10 percent in 1994 and 1995, 

and remained high at 9.9 percent in 

1996 and 1997. 

The petition notes that the cause of 

the eggshell thinning is not known at 

this time. While chlordane and DDE 

were the most frequently detected 

organochlorines in fish sampled near 

eagle nests, they were present at levels 

below those associated with eggshell 

thinning in bald eagles. The petition 

further notes that studies found that 

trace elements, especially mercury, were 

elevated, as were aluminum, arsenic, 

copper, and zinc (Hunt et al. 1992; King 

et al. 1991). 

Response to the Petition 

AGFD (2006c, p. 23) notes that 

eggshell thinning equaled or exceeded 

10 percent on 5 separate occasions 

between 1993 and 2004. These occurred 

in 1994 at 10.7 percent, 1999 at 10.8 

percent, in 2000 at 12.3 percent, in 2003 

at 10.7 percent, and in 2004 at 10.0 

percent. However, AGFD (2006c, p. 23) 

concludes that, since the ban of DDT in 

1973, other factors may have a greater 

influence on productivity than DDT, but 

that egg collection and eggshell 

measurements will continue to ensure 

that the effects of DDT and other 

organochlorines do not affect 

productivity. We agree with this 

conclusion, and believe that eggshell 

thinning warrants further study and 

monitoring; however, at this time, we 

are not aware of any data to indicate 

thinning at the levels cited is resulting 

in losses of eggs. We find that the 

petition did not provide substantial 

information to indicate eggshell 

thinning may place the Sonoran Desert 

bald eagle population in danger of 

becoming extinct. 

Finding 

We have reviewed the petition, 

literature cited in the petition, and 

information in our files. In evaluating 

this petition, we sought to determine if 

sufficient information was provided to 

warrant continued consideration and 

development of a 12-month finding. We 

find available genetic studies on bald 

eagles are dated, the sample size was 

small, and researchers conducting the 

studies found the results to be 

inconclusive. We therefore believe that 

the best available genetic information is 

inconclusive with regard to the 

discreteness of the Sonoran Desert bald 

eagle population. However, we believe 

the petition presents substantial 

information on distinct morphological 

features of the Sonoran Desert bald 

eagles with respect to size. Additionally, 

we believe the petition provides 

substantial information on natal site 

fidelity in breeding birds and the 

limited number of other eagles in 

neighboring southwestern states or 

Mexico. Finally, we believe the 

strongest argument presented by the 

petitioners for a positive discreteness 

finding is provided by the data 

indicating that 20 years of monitoring 

have resulted in the determination that 

no eagles have immigrated to and only 

one eagle has emigrated from the 

Sonoran Desert bald eagle population. 

These three factors lead us to find that 

the petition contains substantial 

information that the Sonoran Desert 

bald eagle population may be discrete 

from other bald eagle populations. 

However, on the basis of our review, 

we find that the petition does not 

present substantial scientific or 

commercial information to indicate that 

the Sonoran Desert bald eagle 

constitutes a valid DPS, pursuant to the 

DPS policy (FR 61 4722). Although we 

believe the population to be discrete, 

the petition does not present substantial 

scientific information that the Sonoran 

Desert bald eagle may be significant in 

relation to the remainder of the taxon. 

Therefore, we conclude that the 

Sonoran Desert population is not a 

listable entity pursuant to section 3(15) 

of the Act. However, recognizing the 

volume of information provided in the 

petition, and the national importance of 

the bald eagle, we conducted a threats 

analysis. 

We find that the petition contains 

detailed information on numerous 

threats affecting the Sonoran Desert 

population of bald eagles. Largely, we 

are in agreement that these threats are 

present, and in some cases are having 

some level of effect on Sonoran Desert 

bald eagles. However, as we discuss 

throughout our responses, no new 

information on threats was presented by 

the petitioner. Additionally, we did not 

find that the petition presented 

substantial information indicating an 

increased level of any of the threats 

discussed. The lack of information on 

new or escalating threats, combined 

with the increased number of occupied 

breeding areas and increased 

productivity levels, causes us to 

conclude that the Sonoran Desert bald 

eagle population, while facing threats, 

continues to increase in numbers of 

adult birds and in productivity. We 

therefore find that the petition did not 

provide substantial information to lead 

us to conclude that the petitioned action 

to reclassify the Sonoran Desert bald 

eagle as endangered may be warranted. 

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). 

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: August 21, 2006. 

H. Dale Hall, 

Director, Fish and Wildlife Service. 

[FR Doc. 06–7180 Filed 8–29–06; 8:45 am] 

BILLING CODE 4310–55–P 


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