Animal Diversity Web

Ge­o­graphic Range

Bald ea­gles (Hali­aee­tus leu­co­cephalus) are found through­out North Amer­ica, near large water sources. These birds are na­tive to Canada, the United States, por­tions of Mex­ico and sev­eral is­lands in­clud­ing Saint Pierre and Miquelon. Pop­u­la­tions are es­pe­cially con­cen­trated in Florida, Alaska, the Pa­cific North­west and near some rivers and lakes in the Mid­west. Pop­u­la­tions may be lim­ited in Mex­ico, Ari­zona, New Mex­ico, Rhode Is­land and Ver­mont. These birds may be va­grants in Be­lize, Bermuda, Puerto Rico and the Vir­gin Is­lands; like­wise, there have been re­ports of bald eagle sight­ings in Ire­land, Swe­den, Siberia, Green­land and north­east­ern Asia. (Alder­fer, 2006; Birdlife In­ter­na­tional, 2012; Buehler, 2000; Cur­nutt and Robert­son Jr, 1994; Dick­in­son, 1991; Gill, 2007; Kauf­man, 2000)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Bald ea­gles typ­i­cally pre­fer areas near large water bod­ies such as sea coasts, coastal es­tu­ar­ies and in­land lakes and rivers, in many areas, these birds are found within 3 km of a water source. Al­though their spe­cific habi­tats may vary de­pend­ing on their range, habi­tat se­lec­tion de­pends largely on prey avail­abil­ity, the avail­abil­ity of tall trees and the de­gree of human dis­tur­bance. These birds avoid human recre­ation areas, bald ea­gles will even forgo feed­ing if their for­ag­ing area is being dis­turbed by hu­mans. Al­though food avail­abil­ity is im­por­tant to habi­tat se­lec­tion, bald ea­gles will in­habit areas fur­ther from for­ag­ing grounds to avoid human in­ter­ac­tion. Most pop­u­la­tions, specif­i­cally those in north­ern re­gions, mi­grate to south­ern, milder cli­mates an­nu­ally. Gen­er­ally, these birds nest in the canopy of tall, conif­er­ous trees, sur­rounded by smaller trees, how­ever, in south­ern Florida, man­groves are used in­stead, they have also been re­ported nest­ing on the ground, on cliffs, on cel­lu­lar phone tow­ers, on elec­tri­cal poles and in ar­ti­fi­cial nest­ing tow­ers. In the Chesa­peake Bay area, these birds often roost in oak trees (Quer­cus) and yel­low poplars (Liri­o­den­dron tulip­ifera), gen­er­ally in wood­lots with good canopy cover; how­ever, their large body size pre­vents their move­ment through closed canopies. Due to food avail­abil­ity, these birds may also be spot­ted near dams and land­fills. (An­drews and Mosher, 1982; Brown, et al., 1998; Buehler, et al., 1991; Cross­ley, 2011; Cur­nutt and Robert­son Jr, 1994; Dick­in­son, 1991; Keis­ter Jr, et al., 1985; Mill­sap, et al., 2004; Saalfeld and Con­way, 2010; Sib­ley, 2003; Stal­mas­ter and Kaiser, 1998)

• Habitat Regions
• temperate

• Terrestrial Biomes
• forest
• mountains

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• coastal

• Other Habitat Features
• estuarine

Phys­i­cal De­scrip­tion

These iconic birds go through 4 dis­tinct mat­u­ra­tion stages, each com­pris­ing one year of their life. Im­me­di­ately after hatch­ing, bald ea­gles have dark eyes, with pink legs and skin and flesh col­ored talons, their skin dark­ens to a bluish hue and their legs be­come yel­low within the first 18 to 22 days of their life. Through­out their first year, their bod­ies, eyes and beaks are dark brown, al­though their un­der­wing coverts and ax­il­lar­ies are white. In their 2nd year, their eyes lighten, be­com­ing gray­ish-brown, they de­velop a light col­ored su­per­cil­iary line and their body be­comes mot­tled white. Dur­ing their 3rd year, their bills and eyes begin to turn yel­low and the col­oration of their head feath­ers lighten, al­though their body re­mains mot­tled. In their 4th year, their body be­comes mostly dark and their head and tail be­come mostly white, with some beige around their eyes and crown and iso­lated dark spots on their tail. Fi­nally, ma­ture col­oration is reached in their 5th year. Im­ma­ture bald ea­gles are often con­fused with golden ea­gles due to their dark col­oration. These birds can be dif­fer­en­ti­ated based on the blotchy white col­oration found on the un­der­wing coverts, ax­il­lar­ies and tails of im­ma­ture bald ea­gles; like­wise, bald ea­gles have longer heads and shorter tails. (Alder­fer, 2006; Bor­tolotti, 1984a; Bor­tolotti, 1984b; Dick­in­son, 1991; Sib­ley, 2003)

Adult bald ea­gles are ex­tremely large birds with char­ac­ter­is­ti­cally yel­low eyes and bills, white heads and tails and dark brown bod­ies, which may ap­pear al­most black. Al­though these birds ob­tain their adult plumage dur­ing their 5th year, they may con­tinue to have a few dark spots on their head and tail for sev­eral ad­di­tional years. Bald ea­gles have sex­u­ally monomor­phic plumage col­oration, al­though fe­males gen­er­ally have a some­what larger body size. These birds have ex­tremely large, pow­er­ful bod­ies; gen­er­ally their plank-like wings have a span of 178 to 229 cm, their bod­ies are 79 to 94 cm long and they weigh about 4.3 kg. Their plumage alone weighs about 700 grams, which is twice as much as their skele­ton, if lost; their flight feath­ers may take 2 to 3 years to re­place. These birds also have large heads, necks, bills and feet with sharp talons. (Alder­fer, 2006; Bor­tolotti, 1984a; Cross­ley, 2011; Dick­in­son, 1991; Gill, 2007; Kauf­man, 2000; Sib­ley, 2003)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

• Average mass

  4.3 kg

  9.47 lb

• Average mass

  3175 g

  111.89 oz

  AnAge

• Range length

  79 to 94 cm

  31.10 to 37.01 in

• Range wingspan

  178 to 229 cm

  70.08 to 90.16 in

Re­pro­duc­tion

Bald ea­gles have a monog­a­mous mat­ing sys­tem. These birds are be­lieved to mate for life, or until a pair mem­ber dies. Al­though they do not mi­grate with their mate, they per­form ex­tremely demon­stra­tive dis­plays when they come to­gether for the breed­ing sea­son. Bald ea­gles per­form flight dis­plays with their mates, swoop­ing at each other. Dur­ing their cart-wheel dis­play, the birds clasp their feet in the air and spin as they plum­met to­wards the ground, let­ting go be­fore im­pact. (Burnie and Wil­son, 2001; Gill, 2007)

• Mating System
• monogamous

Bald ea­gles begin breed­ing when they are 5 years old. Males and fe­males con­struct their nests to­gether, about 1 to 3 months prior to egg lay­ing. Bald eagle nests are com­posed of sticks and can be mas­sive, as birds often reuse nests for con­sec­u­tive years, con­tin­u­ally adding to it each year. The largest bald eagle nest on record was found in Florida; it was used for 30 years and weighed 2 tons when it fell out of a tree. How­ever, nests do not gen­er­ally last that long, on av­er­age nests in south­ern Florida and Saskatchewan are used for 5 years and nests in Alaska are used an av­er­age of 13 years. Nest are gen­er­ally lo­cated away from human set­tle­ments, near water in conif­er­ous trees, but may also be found in man­grove trees, de­cid­u­ous trees, on the ground, on cel­lu­lar phone tow­ers, on elec­tri­cal poles, on cliffs and in ar­ti­fi­cial nest­ing tow­ers, this varies based on the pop­u­la­tion’s lo­ca­tion. Nest­ing dates vary re­gion­ally; in Florida, they begin nest build­ing in Sep­tem­ber, in Ohio they begin in Feb­ru­ary and in Alaska they begin in Jan­u­ary. (Alder­fer, 2006; An­drews and Mosher, 1982; Buehler, 2000; Burnie and Wil­son, 2001; Cross­ley, 2011; Cur­nutt and Robert­son Jr, 1994; Dick­in­son, 1991; Gill, 2007; Jenk­ins and Jack­man, 2006; Mill­sap, et al., 2004; Saalfeld and Con­way, 2010; Watts and Duerr, 2010)

Bald ea­gles typ­i­cally pro­duce 1 brood of 1 to 3 eggs per sea­son; many of their eggs do not sur­vive, al­though they may have re­place­ment clutches if needed. These birds have a low fe­cun­dity, in Cal­i­for­nia, bald ea­gles may pro­duce up to 36 young in their life­time, for males, this is sig­nif­i­cantly cor­re­lated to their body size. The tim­ing of lay­ing varies re­gion­ally. Eggs are in­cu­bated in Florida be­gin­ning in Oc­to­ber and may last until April, whereas in Yel­low­stone, eggs are in­cu­bated from March until April. Pop­u­la­tions lo­cated fur­ther north tend to have shorter breed­ing sea­sons and more syn­chro­nous nest­ing pe­ri­ods. Their eggs are round to oval and are gen­er­ally whitish; in­di­vid­u­als in higher lat­i­tudes often pro­duce larger eggs. Re­gard­less of their ge­o­graphic lo­ca­tion, eggs are gen­er­ally in­cu­bated for about 35 days, fol­lowed by an 11 to 12 week nestling pe­riod. Bald ea­gles are the largest semi-al­tri­cial birds in North Amer­ica and weigh ap­prox­i­mately 60 grams at hatch­ing; they may gain up to 180 grams per day. Fledg­ling time varies ge­o­graph­i­cally; these birds leave the nest when they are be­tween 8 and 14 weeks old, al­though they may re­main de­pen­dent until they are 18 weeks old. (Bor­tolotti, 1984b; Buehler, 2000; Burnie and Wil­son, 2001; Gill, 2007; Jenk­ins and Jack­man, 2006; Mill­sap, et al., 2004; Wood, et al., 1998)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• Breeding interval

  Bald eagles produce one brood per year.

• Breeding season

  The breeding season varies regionally; northern ranges have shorter breeding seasons.

• Range eggs per season

  1 to 3

• Average eggs per season

  2

  AnAge

• Average time to hatching

  35 days

• Average time to hatching

  35 days

  AnAge

• Range fledging age

  8 to 14 weeks

• Range time to independence

  18 (high) weeks

• Average age at sexual or reproductive maturity (female)

  5 years

• Average age at sexual or reproductive maturity (female)
  Sex: female

  1460 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  5 years

• Average age at sexual or reproductive maturity (male)
  Sex: male

  1460 days

  AnAge

Both par­ents care for their off­spring, al­though a larger bur­den falls on the fe­male. Eggs are brooded by fe­males about 3 to 7 times more fre­quently than by males. Eggs are gen­er­ally only ex­posed while the par­ents change po­si­tions or turn the eggs, usu­ally for less than one minute at a time, but it may be longer in mild weather. Dur­ing the nestling pe­riod, young are fed 4 to 5 times per day. Nestling young are brooded con­stantly until they are about 4 weeks old; fe­males are pre­sent about 90% of that time, as op­posed to 50% among males. Most of the food is brought to the nest by males dur­ing the first two weeks post-hatch­ing; even­tu­ally fe­males also pro­vide much of the food. The age at fledg­ing may vary ge­o­graph­i­cally based on cli­mate and food avail­abil­ity, but gen­er­ally ranges be­tween 8 and 14 weeks. Even after fledg­ing, im­ma­ture bald ea­gles may con­tinue their de­pen­dency on their par­ents for an ad­di­tional 4 to 11 weeks. (Bryan Jr, et al., 2005; Buehler, 2000; Burnie and Wil­son, 2001; Gill, 2007; Wood, et al., 1998)

• Parental Investment
• altricial
• male parental care
• female parental care
• pre-fertilization
  • provisioning
  • protecting
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• post-independence association with parents

Lifes­pan/Longevity

Bald ea­gles are long-lived with low adult mor­tal­ity rates, al­though many of their eggs do not sur­vive. A study in Florida found that a year after fledg­ing, im­ma­ture bald ea­gles have a sur­vival rate of 89% in rural habi­tats and 65 to 72% in sub­ur­ban habi­tats. After their 1st year, birds have an an­nual sur­vival rate of 84 to 90%, re­gard­less of their habi­tat type. In north­ern Cal­i­for­nia, adult birds tend to have a 90% an­nual sur­vival rate. These birds have an es­ti­mated cap­tive lifes­pan of 20 to 30 years, al­though one cap­tive in­di­vid­ual re­port­edly sur­vived for 47 years. Among wild in­di­vid­u­als, bald ea­gles in Yel­low­stone are es­ti­mated to have a 15.4 year life ex­pectancy, whereas in Prince William Sound, wild ea­gles are ex­pected to sur­vive about 19 years, with no dif­fer­ence in male and fe­male life spans. The old­est known bald eagle in the wild was found in Alaska and sur­vived 28 years, in north­ern Cal­i­for­nia, the old­est known eagle sur­vived 22 years. Their deaths are often caused by an­thro­pogenic fac­tors such as elec­tro­cu­tion, ve­hi­cle col­li­sions, get­ting caught in legs traps and ac­ci­den­tal poi­son­ing. Nat­ural causes of death in­clude star­va­tion, mal­nour­ish­ment, dis­ease and trauma caused by vi­o­lent weather. (Gill, 2007; Han­cock, 1973; Jenk­ins and Jack­man, 2006; Mc­Clel­land, et al., 1994; Mill­sap, et al., 2004; Schempf, 1997; Travsky and Beau­vais, 2004)

• Range lifespan
  Status: wild

  28 (high) years

• Range lifespan
  Status: captivity

  47 (high) years

• Typical lifespan
  Status: wild

  15 to 20 years

• Typical lifespan
  Status: captivity

  20 to 30 years

Be­hav­ior

The mi­gra­tory be­hav­ior of bald ea­gles varies across their ge­o­graphic ranges. For in­stance, some pop­u­la­tions, such as those from Yel­low­stone, only mi­grate lo­cally for in­creased for­ag­ing op­por­tu­ni­ties and many south­ern pop­u­la­tions do not mi­grate at all. Mi­gra­tory birds from Cana­dian pop­u­la­tions typ­i­cally travel south to the United States dur­ing the win­ter, like­wise, pop­u­la­tions nest­ing in the Great Lakes re­gion may move to­ward the At­lantic coast, down to the Chesa­peake Bay and pop­u­la­tions from north­east­ern United States and Canada may move south and in­land, to­ward the Ap­palachian Moun­tains. Mi­gra­tory birds con­gre­gate in areas with food abun­dances, specif­i­cally those areas below the freeze line with open water for hunt­ing. Many pop­u­la­tions use ge­o­graphic land­marks for nav­i­ga­tion, such as moun­tain ranges and rivers; the Mis­sis­sippi River in par­tic­u­lar is a major mi­gra­tory cor­ri­dor. Im­ma­ture birds have much more er­ratic mi­gra­tory paths and pat­terns. While mi­grat­ing, birds gen­er­ally soar, be­gin­ning in the late morn­ing and go back to roost­ing be­fore dark. Birds from the upper Mid­west may travel any­where from 6 to 151 days to reach their sum­mer range and 15 to 77 days to reach their win­ter­ing range. Birds re­turn to their nest­ing sites at vary­ing times, as soon as weather al­lows. (Alder­fer, 2006; Buehler, 2000; Cross­ley, 2011; Man­der­nack, et al., 2012; Mc­Clel­land, et al., 1994; Mill­sap, et al., 2004; Sib­ley, 2003)

Bald ea­gles are often soli­tary, al­though they pair bond dur­ing the nest­ing sea­son. How­ever, groups of bald ea­gles may be seen in areas with ample prey and they may roost com­mu­nally in large groups of up to 400 in­di­vid­u­als. Their wings are pow­er­ful, al­though bald ea­gles often choose to soar using slow, heavy wing beats, which allow them to travel far dis­tances. When walk­ing, bald ea­gles are some­what awk­ward, rock­ing their bod­ies as they move. A gen­eral time bud­get among bald ea­gles in­cludes the per­cent­age of time rest­ing (91%), drink­ing (2.6%), scav­eng­ing (2.3%) and pi­rat­ing food from oth­ers (1.8%). Gen­er­ally, these birds are less ac­tive dur­ing the win­ter, or when winds are es­pe­cially high, like­wise, pre­cip­i­ta­tion has a neg­a­tive im­pact on their for­ag­ing suc­cess. Dur­ing the breed­ing sea­son, bald ea­gles be­come ter­ri­to­r­ial; vo­cal­iz­ing or chas­ing con­specifics. (Alder­fer, 2006; Buehler, 2000; Cross­ley, 2011; El­liott, et al., 2006; Keis­ter Jr, et al., 1985; Sib­ley, 2003)

• Key Behaviors
• arboreal
• diurnal
• motile
• migratory
• solitary

• Range territory size

  0.5 (low) km^2

• Average territory size

  1-2 km^2

Home Range

Their home range sizes may vary. For in­stance, pop­u­la­tions in Ore­gon and Wash­ing­ton have home ranges of 6 to 47 km2, with an av­er­age of 22 km2; how­ever, a pop­u­la­tion in Alaska has a ter­ri­tory ra­dius of 0.5 km2, this is be­lieved to be the lower limit for the species. On av­er­age, their home range size is be­lieved to be 1 to 2 km2 and does not ap­pear to os­cil­late be­tween breed­ing and non-breed­ing sea­sons. (Gar­rett, et al., 1993; Travsky and Beau­vais, 2004)

Com­mu­ni­ca­tion and Per­cep­tion

Con­trary to pop­u­lar per­cep­tion, bald ea­gles have rel­a­tively weak, high pitched, thin vo­cal­iza­tions, com­posed of chirps, whis­tles and harsh chat­ters. These birds pro­duce 3 main types of calls, a chat­ter, which sounds like ‘kwit, kwit, kwit, kwit, kee-kee-kee-kee-ker’, a wail and a peal, which is a long, high-pitched cry used when threats are per­ceived. In ad­di­tion, these birds may com­mu­ni­cate threats with a se­ries of vi­sual dis­plays such as head mo­tions, wing mo­tions and crouch­ing. Breed­ing pairs vo­cal­ize to each other when re­turn­ing to their nest and have tremen­dous fly­ing dis­plays. With large, for­ward fac­ing eyes, bald ea­gles likely have very good binoc­u­lar vi­sion. Al­though these birds do not have an adept sense of smell, they do avoid food items that taste spoiled. (Alder­fer, 2006; Belet­sky, 2006; Buehler, 2000; Burnie and Wil­son, 2001; Gill, 2007; Hansen, 1986; Kauf­man, 2000; Sib­ley, 2003)

• Communication Channels
• visual
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

As op­por­tunis­tic for­agers, bald ea­gles have a fairly wide diet, but gen­er­ally pre­fer fish. With such a large range, their diet may vary greatly. Bald ea­gles are known to eat the fol­low­ing fish: rain­bow trout, Amer­i­can eels, giz­zard shads, white cat­fish, koka­nee salmon, rock green­lings, Pa­cific cod, atka mack­erel, large mouth bass and chum salmon, among oth­ers. The speed of a river flow can greatly im­pact an ea­gles hunt­ing suc­cess. These birds do not sub­merge them­selves to ob­tain prey; in­stead, they use their strong talons to re­move fish near the water sur­face. An­other large com­po­nent of their diet in­cludes adult water birds, their nestlings and their eggs in­clud­ing com­mon mur­res, great blue herons, snow geese, Ross geese, tun­dra swans, north­ern ful­mars, auk­lets, Amer­i­can coots and com­mon loons. In the win­ter, their diets often shift to car­rion and small mam­mal prey. Bald ea­gles may hunt live ground squir­rels, mon­tane voles, Nor­way rats and sea otter pups, among oth­ers. Like­wise, these birds feed on the car­rion of large mam­mals such as elk, moose, mule deer, cari­bou, bison, wolves and arc­tic foxes. Pop­u­la­tions of bald ea­gles have also been found re­sid­ing near land­fills, con­sum­ing human refuse. In ad­di­tion to for­ag­ing by pur­su­ing live prey or con­sum­ing car­rion, these birds often pi­rate food from con­specifics and other rap­tor species, such as os­preys. In gen­eral, younger and smaller birds choose to hunt in­stead of pi­rate. When hunt­ing, these birds perch and ob­serve be­fore de­scend­ing on their prey and lift­ing it from the ground with their talons, how­ever, when pi­rat­ing food; ea­gles may fly, leap or walk to snatch the food. Re­gard­less, bald ea­gles tend to for­age much less when dis­turbed by hu­mans, at times when hu­mans are ac­tive in for­ag­ing areas, their feed­ing may be re­duced by as much as 35%. For many pop­u­la­tions, their ar­rival to their sum­mer­ing grounds marks a time of min­i­mal food avail­abil­ity be­cause many of the water sources may still be frozen. For­tu­nately, these birds can sur­vive with­out food for sev­eral days. When food is avail­able, bald ea­gles often gorge and store food in their crop for later di­ges­tion. (Alder­fer, 2006; An­thony, et al., 2008; Brown, 1993; Brown, et al., 1998; Bryan Jr, et al., 2005; Buehler, 2000; Burnie and Wil­son, 2001; Dick­in­son, 1991; El­liott, et al., 2006; Hansen, 1986; Har­vey, et al., 2012; Kauf­man, 2000; Ko­rhel and Clark, 1981; Mc­Carthy, et al., 2010; Mc­Clel­land, et al., 1994; Nor­man, et al., 1989; Par­rish, et al., 2001; Sib­ley, 2003; Stal­mas­ter and Kaiser, 1998; Thomp­son, et al., 2005)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates
  • piscivore

• Animal Foods
• birds
• mammals
• fish
• eggs
• carrion

Pre­da­tion

For some pop­u­la­tions, bald ea­gles have few preda­tors, al­low­ing them to nest on the ground. How­ever, their eggs and young are often preyed upon by mag­pies, gulls, ravens, crows, black bears, rac­coon, bob­cats, wolver­ines and arc­tic foxes. Fully grown adult birds are not often sub­ject to pre­da­tion. (Buehler, 2000; Cur­nutt and Robert­son Jr, 1994)

• Known Predators

  • magpies Corvidae
  • gulls (Laridae)
  • ravens (Corvus)
  • crows (Corvus)
  • black bears (Ursus americanus)
  • raccoon (Procyon lotor)
  • bobcats (Lynx rufus)
  • wolverines (Gulo gulo)
  • arctic foxes (Vulpes lagopus)

Ecosys­tem Roles

As a top preda­tor, bald ea­gles im­pact all mem­bers of their trophic com­mu­nity. Their de­cline and re­cent pop­u­la­tion resur­gence has im­pacted many other or­gan­isms, they are even caus­ing a pop­u­la­tion de­cline in com­mon mur­res. These birds have been found with Tox­o­plasma gondii as well as a pro­to­zoan, 2 gen­era of trema­todes, 1 genus of acan­tho­cepha­lan and 7 gen­era of ne­ma­todes. (Buehler, 2000; Par­rish, et al., 2001; Szabo, et al., 2004)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Bald ea­gles have been the na­tional sym­bol of the United States since 1782. As a highly charis­matic species, bald ea­gles draw bird watch­ers and other na­ture en­thu­si­asts. In 1989, it was es­ti­mated that 20 to 30 mil­lion peo­ple are in­volved in bird watch­ing ac­tiv­i­ties, which may equate to ap­prox­i­mately 20 bil­lion dol­lars an­nu­ally. (Burnie and Wil­son, 2001; Hvene­gaard, et al., 1989; Kauf­man, 2000; Loomis and White, 1996)

• Positive Impacts
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Bald ea­gles do not di­rectly have a neg­a­tive im­pact on hu­mans. How­ever, as a method of habi­tat man­age­ment, buffer zones were es­tab­lished around their nest­ing sites, which lim­its human de­vel­op­ment in some areas. (Birdlife In­ter­na­tional, 2012; Mill­sap, et al., 2004; Stal­mas­ter and Kaiser, 1998; Wood, et al., 1998)

Con­ser­va­tion Sta­tus

The con­ser­va­tion sta­tus of bald ea­gles has shifted greatly dur­ing the re­cent past. As of June 28, 2007 these birds were re­moved from the pro­tec­tion of the En­dan­gered Species Act where they had been listed since 1978. Their pop­u­la­tion was neg­a­tively im­pacted in the early and mid- 1900’s by hunt­ing, habi­tat de­struc­tion and the use of in­sec­ti­cides, such as DDT. The Bald Eagle Pro­tec­tion Act was put into ef­fect in 1940, al­though their pop­u­la­tions con­tin­ued to de­cline through­out the 1950’s and 70’s. DDT’s fat sol­u­ble prop­er­ties allow it to ac­cu­mu­late in the fats of or­gan­isms, be­cause it bi­o­log­i­cally mag­ni­fies, top preda­tors, such as bald ea­gles, were at great risk. DDT im­pacts all an­i­mals, with im­pacts such as de­for­mi­ties, neu­ro­log­i­cal dam­age and in the case of birds, brit­tle egg shells and un­hatch­ing eggs. For­tu­nately, after the ban of DDT in 1972, their pop­u­la­tion has in­creased dra­mat­i­cally. In 1963, there were an es­ti­mated 417 pairs of bald ea­gles re­main­ing in the con­ti­nen­tal US, as of 1998, there were 5,748 pairs, bring­ing their pro­duc­tiv­ity back to lev­els seen prior to DDT usage. In ad­di­tion, their pop­u­la­tion in Alaska as of 1993 was be­tween 20 and 25,000 in­di­vid­u­als. In Wash­ing­ton State, these birds have had a 700% pop­u­la­tion in­crease from 1981 to 2005, grow­ing ap­prox­i­mately 9% an­nu­ally. Other fac­tors, such as guide­lines re­gard­ing the prox­im­ity in which hu­mans can de­velop near bald eagle nests have also pos­i­tively im­pacted the species' pop­u­la­tion. Bald ea­gles are cur­rently listed as a species of least con­cern ac­cord­ing to the IUCN Red List of Threat­ened Species due to their in­creas­ing pop­u­la­tion and large range. Cur­rent and fu­ture threats to this species in­clude con­t­a­m­i­na­tion from coal power plants, Mer­cury poi­son­ing and global cli­mate change. (Birdlife In­ter­na­tional, 2012; Carl­son, et al., 2012; Gill, 2007; Grubb, et al., 1990; Har­vey, et al., 2012; Mill­sap, et al., 2004; Rock­well, 1998; Saalfeld and Con­way, 2010; Schi­rato and Par­son, 2006; Starr and Tag­gart, 2006; Thomp­son, et al., 2005; Watts and Duerr, 2010; Watts, et al., 2006; Watts, et al., 2008; Wood, et al., 1998)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  No special status

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Leila Si­cil­iano Mar­tina (au­thor), An­i­mal Di­ver­sity Web Staff.

Ref­er­ences

Alder­fer, J. 2006. Com­plete Birds of North Amer­ica. Wash­ing­ton, D.C: The Na­tional Ge­o­graphic So­ci­ety.

An­drews, J., J. Mosher. 1982. Bald eagle nest site se­lec­tion and nest­ing habi­tat in Mary­land. The Jour­nal of Wildlife Man­age­ment, 46-2: 383-390.

An­thony, R., J. Estes, M. Ricca, A. Miles, E. Fors­man. 2008. Bald ea­gles and sea ot­ters in the Aleut­ian Arch­i­pel­ago: In­di­rect ef­fects of trophic cas­cades. Ecol­ogy, 89-10: 2725-2735.

Belet­sky, L. 2006. Bird Songs. San Fran­cisco: Chron­i­cle Books.

Birdlife In­ter­na­tional, 2012. "Hali­aee­tus leu­co­cephalus" (On-line). IUCN Red List of Threat­ened Species. Ac­cessed Au­gust 05, 2013 at www.​iucnredlist.​org.

Bor­tolotti, G. 1984. Phys­i­cal de­vel­op­ment of nestling bald ea­gles with em­pha­sis on the tim­ing of growth events. The Wil­son Bul­letin, 96-4: 524-542.

Bor­tolotti, G. 1984. Sex­ual size di­mor­phism and age-re­lated size vari­a­tion in bald ea­gles. The Jour­nal of Wildlife Man­age­ment, 48-1: 72-81.

Brown, B. 1993. Win­ter for­ag­ing ecol­ogy of bald ea­gles in Ari­zona. The Con­dor, 95-1: 132-138.

Brown, B., L. Stevens, T. Yates. 1998. In­flu­ences of fluc­tu­at­ing river flows on bald eagle for­ag­ing be­hav­ior. The Con­dor, 100-4: 745-748.

Bryan Jr, A., L. Hop­kins, C. El­dridge, I. Bris­bin Jr, C. Jagoe. 2005. Be­hav­ior and food habits at a bald eagle nest in in­land South Car­olina. South­east­ern Nat­u­ral­ist, 4-3: 459-468.

Buehler, D. 2000. "Bald Eagle (Hali­aee­tus leu­co­cephalus)" (On-line). The Birds of North Amer­ica On­line. Ac­cessed Au­gust 05, 2013 at http:bna.​birds.​cornell.​edu.​prox.​lib.​umich.​edu/​bna/​species/​506.

Buehler, D., T. Mers­mann, J. Fraser, J. See­gar. 1991. Non­breed­ing bald eagle com­mu­nal and soli­tary roost­ing be­hav­ior and roost habi­tat on the north­ern Chesa­peake Bay. The Jour­nal of Wildlife Man­age­ment, 55-2: 273-281.

Burnie, D., D. Wil­son. 2001. An­i­mal. New York: DK Pub­lish­ing.

Carl­son, J., A. Har­mata, M. Restani. 2012. En­vi­ron­men­tal con­t­a­m­i­nants in nestling bald ea­gles pro­duced in Mon­tana and Wyoming. Jour­nal of Rap­tor Re­search, 46-3: 274-282.

Cross­ley, R. 2011. The Cross­ley ID Guide: East­ern Birds. Prince­ton, New Jer­sey: Prince­ton Uni­ver­sity Press.

Cur­nutt, J., W. Robert­son Jr. 1994. Bald eagle nest site char­ac­ter­is­tics in south Florida. The Jour­nal of Wildlife Man­age­ment, 58-2: 218-221.

Dick­in­son, M. 1991. Field Guide to the Birds of North Amer­ica. Wash­ing­ton, D.C: The Na­tional Ge­o­graphic So­ci­ety.

El­liott, K., J. Duffe, S. Lee, P. Mineau, J. El­liott. 2006. For­ag­ing ecol­ogy of bald eagle at an urban land­fill. The Wil­son Jour­nal of Or­nithol­ogy, 118-3: 380-390.

Gar­rett, M., J. Wat­son, R. An­thony. 1993. Bald eagle home range and habi­tat use in the Co­lum­bia River Es­tu­ary. Jour­nal of Wildlife Man­age­ment, 57-1: 19-27.

Gill, F. 2007. Or­nithol­ogy. New York: W.H Free­man and Com­pany.

Grubb, T., S. Wiemeyer, L. Kiff. 1990. Eggshell thin­ning and con­t­a­m­i­nant lev­els in bald eagle eggs from Ari­zona, 1977 to 1985. The South­west­ern Nat­u­ral­ist, 35-3: 298-301.

Han­cock, D. 1973. Cap­tive prop­a­ga­tion of bald ea­gles Hali­aee­tus leu­co­cephalus: A re­view. In­ter­na­tional Zoo Year­book, 13-1: 244-249.

Hansen, A. 1986. Fight­ing be­hav­ior in bald ea­gles: A test of game the­ory. Ecol­ogy, 67-3: 787-797.

Har­vey, C., P. Mo­ri­arty, E. Salathe Jr. 2012. Mod­el­ing cli­mate change im­pacts on over win­ter­ing bald ea­gles. Ecol­ogy and Evo­lu­tion, 2-3: 501-514.

Hvene­gaard, G., J. But­ler, D. Krystofiak. 1989. Eco­nomic val­ues of bird watch­ing at Point Pelee Na­tional Park, Canada. Wildlife So­ci­ety Bul­letin, 17-4: 526-531.

Jenk­ins, J., R. Jack­man. 2006. Life­time re­pro­duc­tive suc­cess of bald ea­gles in north­ern Cal­i­for­nia. The Con­dor, 108: 730-735.

Kauf­man, K. 2000. Kauf­man Field Guide to Birds of North Amer­ica. New York: Houghton Mif­flin Com­pany.

Keis­ter Jr, G., R. An­thony, H. Holbo. 1985. A model of en­ergy con­sump­tion in bald ea­gles: An eval­u­a­tion of night com­mu­nal roost­ing. The Wil­son Bul­letin, 97-2: 148-160.

Ko­rhel, A., T. Clark. 1981. Bald eagle win­ter sur­vey in the Snake River Canyon, Wyoming. The Great Basin Nat­u­ral­ist, 41-4: 461-464.

Loomis, J., D. White. 1996. Eco­nomic ben­e­fits of rare and en­dan­gered species: Sum­mary and meta-analy­sis. Eco­log­i­cal Eco­nom­ics, 18: 197-206.

Man­der­nack, B., M. Solen­sky, M. Martell, R. Schmitz. 2012. Satel­lite track­ing of bald ea­gles in the upper Mid­west. Jour­nal of Rap­tor Re­search, 46-3: 258-273.

Mc­Carthy, K., S. DeSte­fano, T. Laskowski. 2010. Bald eagle pre­da­tion on com­mon loon eggs. Jour­nal of Rap­tor Re­search, 44-3: 249-251.

Mc­Clel­land, B., L. Young, P. Mc­Clel­land, J. Cren­shaw, H. Allen, D. Shea. 1994. Mi­gra­tion ecol­ogy of bald ea­gles from au­tumn con­cen­tra­tions in Glac­ier Na­tional Park, Mon­tana. Wildlife Mono­graphs, 125: 3-61.

Mill­sap, B., T. Breen, E. Mc­Connell, T. Stef­fer, L. Phillips, N. Dou­glas, S. Tay­lor. 2004. Com­par­a­tive fe­cun­dity and sur­vival of bald ea­gles fledged from sub­ur­ban and rural natal areas in Florida. The Jour­nal of Wildlife Man­age­ment, 68-4: 1018-1031.

Nor­man, D., A. Breault, I. Moul. 1989. Bald eagle in­cur­sions and pre­da­tion at great blue heron colonies. Colo­nial Wa­ter­birds, 12-2: 215-217.

Par­rish, J., M. Mar­vier, R. Paine. 2001. Di­rect and in­di­rect ef­fects: In­ter­ac­tions be­tween bald ea­gles and com­mon mur­res. Eco­log­i­cal Ap­pli­ca­tions, 11-6: 1858-1869.

Rock­well, D. 1998. The Na­ture of North Amer­ica: A Hand­book to the Con­ti­nent. New York: Berkley Books.

Saalfeld, S., W. Con­way. 2010. Local and land­scape habi­tat se­lec­tion of nest­ing bald ea­gles in east Texas. South­east­ern Nat­u­ral­ist, 9-4: 731-742.

Schempf, P. 1997. Bald eagle longevity record from south­east­ern Alaska. Jour­nal of Field Or­nithol­ogy, 68-1: 150-151.

Schi­rato, G., W. Par­son. 2006. Bald eagle man­age­ment in ur­ban­iz­ing habi­tat of Puget Sound, Wash­ing­ton. North­west­ern Nat­u­ral­ist, 87:2: 138-142.

Sib­ley, D. 2003. The Sib­ley Field Guide to Birds of East­ern North Amer­ica. New York: Al­fred A. Knopf.

Stal­mas­ter, M., J. Kaiser. 1998. Ef­fects of recre­ational ac­tiv­ity on win­ter­ing bald ea­gles. Wildlife Mono­graphs, 137: 3-46.

Starr, C., R. Tag­gart. 2006. Bi­ol­ogy: The Unity and Di­ver­sity of Life. Bel­mont, Cal­i­for­nia: Thom­son Brooks/ Cole.

Szabo, K., M. Mense, T. Lip­scomb, K. Felix, J. Dubey. 2004. Fatal Tox­o­plas­mo­sis in a bald eagle (Hali­aee­tus leu­co­cephalus). The Jour­nal of Par­a­sitol­ogy, 90-4: 907-908.

Thomp­son, C., P. Nye, G. Schmidt, D. Garcelon. 2005. For­ag­ing ecol­ogy of bald ea­gles in a fresh water tidal sys­tem. The Jour­nal of Wildlife Man­age­ment, 69-2: 609-617.

Travsky, A., G. Beau­vais. 2004. Species as­sess­ment for bald ea­gles (Hali­aee­tus leu­co­cephalus) in Wyoming. United States De­part­ment of the In­te­rior, 1: 1-40.

Watts, B., A. Duerr. 2010. Nest turnover rates and list-frame decay in bald ea­gles: Im­pli­ca­tions for the na­tional mon­i­tor­ing plan. The Jour­nal of Wildlife Man­age­ment, 74-5: 940-944.

Watts, B., A. Markham, M. Bryd. 2006. Salin­ity and pop­u­la­tion pa­ra­me­ters of bald ea­gles (Hali­aee­tus leu­co­cephalus) in the lower Chesa­peake Bay. The Auk, 123-2: 393-404.

Watts, B., G. Ther­res, M. Bryd. 2008. Re­cov­ery of the Chesa­peake Bay bald eagle nest­ing pop­u­la­tions. The Jour­nal of Wildlife Man­age­ment, 72-1: 152-158.

Wood, P., M. Col­lopy, C. Sek­erak. 1998. Post fledg­ing nest de­pen­dence pe­riod for bald ea­gles in Florida. The Jour­nal of Wildlife Man­age­ment, 62-1: 333-339.