The bald eagle is an opportunistic feeder that subsists mainly onfish, upon which it swoops down and snatches from the water with its talons. It builds the largestnest of anyNorth American bird and the largest tree nests ever recorded for any animal species, up to 4 m (13 ft) deep, 2.5 m (8.2 ft) wide, and 1 metric ton (1.1 short tons) in weight.Sexual maturity is attained at the age of four to five years.
Bald eagles are not bald; the name derives from an older meaning of the word, "white-headed". The adult is mainly brown with a white head and tail. The sexes are identical inplumage, but females are about 25% larger than males. The yellow beak is large and hooked. The plumage of the immature is brown.
The bald eagle is thenational bird andnational symbol of theUnited States and appears onits seal. In the late 20th century it was on the brink ofextirpation in the contiguous United States, but measures such as banning the practice of hunting bald eagles and banning the use of the harmful pesticideDDT slowed the decline of their population. Populations have since recovered, and the species' status was downgraded from "endangered" to "threatened" in 1995 and removed from the list altogether in 2007.
Taxonomy
Closeup of the eponymous white head
The bald eagle is placed in the genusHaliaeetus (sea eagles), and gets both its common and specific scientific names from the distinctive appearance of the adult's head.Bald in the English name is from an older usage meaning "having white on the face or head" rather than "hairless", referring to the white head feathers contrasting with the darker body.[4]
The bald eagle was one of the many species originally described byCarl Linnaeus in his 18th-century workSystema Naturae, under the nameFalco leucocephalus.[9]
The bald eagle forms aspecies pair with thewhite-tailed eagle ofEurasia. This species pair consists of a white-headed and a tan-headed species of roughly equal size; the white-tailed eagle also has overall somewhat paler brown body plumage. The two species fill the sameecological niche in their respective ranges. The pair diverged from other sea eagles at the beginning of the EarlyMiocene (c. 10 Ma BP) at the latest, but possibly as early as the Early/MiddleOligocene, 28 Ma BP, if the most ancient fossil record is correctly assigned to thisgenus.[10]
Subspecies
There are two historically recognizedsubspecies of bald eagle,[11][12] although it is believed these may be the same species with size differences according toBergmann's Rule.[13]
H. l. leucocephalus(Linnaeus, 1766) is the nominate subspecies. It is found in the southern United States andBaja California peninsula.[14]
H. l. washingtoniensis(Audubon, 1827), synonymH. l. alascanus(Townsend, 1897), the northern subspecies, is larger than southern nominateleucocephalus. It is found in theNorthern United States,Canada andAlaska.[11][14]
Theplumage of an adult bald eagle is evenly dark brown with a white head andtail. The tail is moderately long and slightly wedge shaped. Males and females are identical in plumage coloration, butsexual dimorphism is evident in the species, in that females are 25% larger than males.[11] Thebeak,feet andirises are bright yellow. The legs are feather free, and the toes are short and powerful with largetalons. The highly developed talon of the hind toe is used to pierce the vital areas of prey while it is held immobile by the front toes.[15] The beak is large and hooked, with a yellowcere.[16] The adult bald eagle is unmistakable in its native range. The closely relatedAfrican fish eagle (Haliaeetus vocifer) (from far outside the bald eagle's range) also has a brown body (albeit of somewhat more rufous hue), white head and tail, but differs from the bald eagle in having a white chest and black tip to the bill.[17]
Bald eagle anatomyAn individual bald eagle at various stages of plumage between nestling and adult. Images show the same bird as a nestling, at 1 year, 2 years, 3 years, 4 years, and 5 years old. Note the lightening of the eye, the yellowing of the beak, and the whitening of the eponymous head.
The plumage of the immature is a dark brown overlaid with messy white streaking until the fifth (rarely fourth, very rarely third) year, when it reaches sexual maturity.[11][15] Immature bald eagles are distinguishable from thegolden eagle (Aquila chrysaetos), the only other very large, non-vulturine raptorial bird inNorth America, in that the former has a larger, more protruding head with a larger beak, straighter edgedwings which are held flat (not slightly raised) and with a stiffer wing beat and feathers which do not completely cover the legs. When seen well, the golden eagle is distinctive in plumage with a more solid warm brown color than an immature bald eagle, with a reddish-golden patch to itsnape and (in immature birds) a highly contrasting set of white squares on the wing.[18]
A bald eagle showing itswingspanCloseup of a museum specimen's foot, showing the toepads' spiny papillae
The bald eagle has sometimes been considered the largest true raptor (accipitrid) in North America. The only larger species of raptor-like bird is theCalifornia condor (Gymnogyps californianus), aNew World vulture that today is not generally considered a taxonomic ally of true accipitrids.[19] However, the golden eagle, averaging 4.18 kg (9.2 lb) and 63 cm (25 in) inwing chord length in its American race (Aquila chrysaetos canadensis), is merely 455 g (1.003 lb) lighter in mean body mass and exceeds the bald eagle in mean wing chord length by around 3 cm (1.2 in).[17][20] Additionally, the bald eagle's close cousins, the relatively longer-winged but shorter-tailedwhite-tailed eagle and the overall largerSteller's sea eagle (Haliaeetus pelagicus), may, rarely, wander to coastalAlaska fromAsia.[17]
The bald eagle has a body length of 70–102 cm (28–40 in). Typical wingspan is between 1.8 and 2.3 m (5 ft 11 in and 7 ft 7 in) and mass is normally between 3 and 6.3 kg (6.6 and 13.9 lb).[17] Females are about 25% larger than males, averaging as much as 5.6 kg (12 lb), and against the males' average weight of 4.1 kg (9.0 lb).[11][21][22][23]
The size of the bird varies by location and generally corresponds withBergmann's rule: the species increases in size further away from the equator and the tropics. For example, eagles fromSouth Carolina average 3.27 kg (7.2 lb) in mass and 1.88 m (6 ft 2 in) in wingspan, smaller than their northern counterparts.[24] One field guide in Florida listed similarly small sizes for bald eagles there, at about 4.13 kg (9.1 lb).[25] Of intermediate size, 117 migrant bald eagles inGlacier National Park were found to average 4.22 kg (9.3 lb) but this was mostly (possibly post-dispersal) juvenile eagles, with six adults here averaging 4.3 kg (9.5 lb).[26] Wintering eagles inArizona (winter weights are usually the highest of the year since, like many raptors, they spend the highest percentage of time foraging during winter) were found to average 4.74 kg (10.4 lb).[27]
The largest eagles are from Alaska, where large females may weigh more than 7 kg (15 lb) and span 2.44 m (8 ft 0 in) across the wings.[16][28] A survey of adult weights in Alaska showed that females there weighed on average 5.35 kg (11.8 lb), respectively, and males weighed 4.23 kg (9.3 lb) against immatures which averaged 5.09 kg (11.2 lb) and 4.05 kg (8.9 lb) in the two sexes.[29][30] An Alaskan adult female eagle that was considered outsized weighed some 7.4 kg (16 lb).[31] R.S. Palmer listed a record from 1876 inWyoming County, New York of an enormous adult bald eagle that was shot and reportedly scaled 8.2 kg (18 lb).[30] Among standard linear measurements, the wing chord is 51.5–69 cm (20.3–27.2 in), thetail is 23–37 cm (9.1–14.6 in) long, and thetarsus is 8 to 11 cm (3.1 to 4.3 in).[17][32] Theculmen reportedly ranges from 3 to 7.5 cm (1.2 to 3.0 in), while the measurement from thegape to the tip of the bill is 7–9 cm (2.8–3.5 in).[32][33] The bill size is unusually variable: Alaskan eagles can have up to twice the bill length of birds from theSouthern United States (Georgia,Louisiana,Florida), with means including both sexes of 6.83 cm (2.69 in) and 4.12 cm (1.62 in) in culmen length, respectively, from these two areas.[34][35]
Thecall consists of weak staccato, chirping whistles,kleek kik ik ik ik, somewhat similar in cadence to agull's call. The calls of young birds tend to be harsher and shriller than those of adults.[17][18]
The bald eagle's natural range covers most ofNorth America, including most ofCanada, all of thecontinental United States, and northernMexico. It is the onlysea eagleendemic to North America. Occupying varied habitats from thebayous ofLouisiana to theSonoran Desert and the eastern deciduous forests ofQuebec andNew England, northern birds aremigratory, while southern birds are resident, remaining on their breeding territory all year. At minimum population, in the 1950s, it was largely restricted toAlaska, theAleutian Islands, northern and eastern Canada, andFlorida.[36] From 1966 to 2015 bald eagle numbers increased substantially throughout its winter and breeding ranges,[37] and as of 2018 the species nests in every continental state and province in theUnited States and Canada.[38]
The majority of bald eagles in Canada are found along theBritish Columbia coast while large populations are found in the forests ofAlberta,Saskatchewan,Manitoba andOntario.[39] Bald eagles also congregate in certain locations in winter. From November until February, one to two thousand birds winter inSquamish, British Columbia, about halfway betweenVancouver andWhistler. In March 2024, bald eagles were found nesting inToronto for the first time.[40] The birds primarily gather along theSquamish andCheakamus Rivers, attracted by thesalmon spawning in the area.[41] Similar congregations of wintering bald eagles at open lakes and rivers, wherein fish are readily available for hunting or scavenging, are observed in theNorthern United States.[42]
It has occurred as avagrant twice inIreland; a juvenile was shot illegally inCounty Fermanagh on January 11, 1973 (misidentified at first as awhite-tailed eagle), and an exhausted juvenile was captured nearCastleisland inCounty Kerry on November 15, 1987.[43] There is also a record of it fromLlyn Coron inAnglesey, United Kingdom, from October 17, 1978;[44] the provenance of this individual eagle has remained in dispute.
Habitat
In flight during a licensed performance inOntario, CanadaDuring training at the Canadian Raptor Conservancy
The bald eagle occurs during its breeding season in virtually any kind of Americanwetland habitat such asseacoasts,rivers, largelakes ormarshes or other large bodies of open water with an abundance offish. Studies have shown a preference for bodies of water with a circumference greater than 11 km (7 mi), and lakes with an area greater than 10 km2 (4 sq mi) are optimal for breeding bald eagles.[45]
The bald eagle typically requires old-growth and mature stands ofconiferous orhardwood trees for perching,roosting, andnesting. Tree species reportedly is less important to the eagle pair than the tree's height, composition and location.[46] Perhaps of paramount importance for this species is an abundance of comparatively large trees surrounding the body of water. Selected trees must have good visibility, be over 20 m (66 ft) tall, an open structure, and proximity to prey. If nesting trees are in standing water such as in amangrove swamp, the nest can be located fairly low, at as low as 6 m (20 ft) above the ground.[47] In a more typical tree standing on dry ground, nests may be located from 16 to 38 m (52 to 125 ft) in height. InChesapeake Bay, nesting trees averaged 82 cm (32 in) in diameter and 28 m (92 ft) in total height, while inFlorida, the average nesting tree stands 23 m (75 ft) high and is 23 cm (9.1 in) in diameter.[48][49] Trees used for nesting in theGreater Yellowstone area average 27 m (89 ft) high.[50] Trees or forest used for nesting should have a canopy cover of no more than 60%, and no less than 20%, and be in close proximity to water.[45] Most nests have been found within 200 m (660 ft) of open water. The greatest distance from open water recorded for a bald eagle nest was over 3 km (1.9 mi), in Florida.[19]
Bald eagle nests are often very large in order to compensate for size of the birds. The largest recorded nest was found in Florida in 1963, and was measured at 2.9 m (9.5 ft) wide and 6.1 m (20 ft) deep.[51]
In Florida, nesting habitats often consist of mangrove swamps, the shorelines of lakes and rivers,pinelands, seasonally floodedflatwoods, hardwoodswamps, and openprairies andpastureland with scattered tall trees. Favored nesting trees in Florida are slash pines (Pinus elliottii),longleaf pines (P. palustris), loblolly pines (P. taeda) andcypress trees, but for the southern coastal areas where mangroves are usually used.[47] InWyoming, groves of maturecottonwoods or tall pines found along streams and rivers are typical bald eagle nesting habitats. Wyoming eagles may inhabit habitat types ranging from large, old-growth stands of ponderosa pines (Pinus ponderosa) to narrow strips of riparian trees surrounded by rangeland.[19] InSoutheast Alaska, Sitka spruce (Picea sitchensis) provided 78% of the nesting trees used by eagles, followed by hemlocks (Tsuga) at 20%.[46] Increasingly, eagles nest in human-made reservoirs stocked with fish.[47]
The bald eagle is usually quite sensitive to human activity while nesting, and is found most commonly in areas with minimal human disturbance. It chooses sites more than 1.2 km (0.75 mi) from low-density human disturbance and more than 1.8 km (1.1 mi) from medium- to high-density human disturbance.[45] However, bald eagles will occasionally nest in large estuaries or secluded groves within major cities, such asHardtack Island on theWillamette River inPortland, Oregon, orJohn Heinz National Wildlife Refuge at Tinicum inPhiladelphia, Pennsylvania, which are surrounded by a great quantity of human activity.[52][53] Even more contrary to the usual sensitivity to disturbance, a family of bald eagles moved to theHarlem neighborhood inNew York City in 2010.[54]
While wintering, bald eagles tend to be less habitat and disturbance sensitive. They will commonly congregate at spots with plentiful perches and waters with plentiful prey and (in northern climes) partially unfrozen waters. Alternately, non-breeding or wintering bald eagles, particularly in areas with a lack of human disturbance, spend their time in various upland, terrestrial habitats sometimes quite far away from waterways. In the northern half of North America (especially the interior portion), this terrestrial inhabitance by bald eagles tends to be especially prevalent because unfrozen water may not be accessible. Upland wintering habitats often consist of open habitats with concentrations of medium-sizedmammals, such as prairies,meadows ortundra, or openforests with regularcarrion access.[19][46]
Behavior
The bald eagle is a powerful flier, and soars onthermal convection currents. It reaches speeds of 56–70 km/h (35–43 mph) when gliding and flapping, and about 48 km/h (30 mph) while carrying fish.[55] Its dive speed is between 120–160 km/h (75–99 mph), though it seldom dives vertically.[56] Regarding their flying abilities, despite being morphologically less well adapted to faster flight thangolden eagles (especially during dives), the bald eagle is considered surprisingly maneuverable in flight. Bald eagles have also been recorded catching up to and then swooping under geese in flight, turning over and thrusting their talons into the other bird's breast.[30] It is partiallymigratory, depending on location. If its territory has access to open water, it remains there year-round, but if the body of water freezes during the winter, making it impossible to obtain food, it migrates to the south or to the coast. A number of populations are subject to post-breeding dispersal, mainly in juveniles; Florida eagles, for example, will disperse northwards in the summer.[57] The bald eagle selects migration routes which take advantage of thermals,updrafts, and food resources. During migration, it may ascend in a thermal and then glide down, or may ascend in updrafts created by the wind against a cliff or other terrain. Migration generally takes place during the daytime, usually between the local hours of 8:00 a.m. and 6:00 p.m., when thermals are produced by the sun.[15]
Diet and feeding
The bald eagle is an opportunisticcarnivore with the capacity to consume a great variety of prey.Fish often comprise most of the eagle's diet throughout their range.[58] In 20 food habit studies across the species' range, fish comprised 56% of the diet of nesting eagles,birds 28%,mammals 14% and other prey 2%.[59] More than 400 species are known to be included in the bald eagle's prey spectrum, far more than its ecological equivalent in theOld World, thewhite-tailed eagle, is known to take. Despite its considerably lower population, the bald eagle may come in second amongst all North American accipitrids, slightly behind only thered-tailed hawk, in number of prey species recorded.[30][59][60][61]
To hunt fish, the eagle swoops down over the water and snatches the fish out of the water with itstalons. They eat by holding the fish in one claw and tearing the flesh with the other. Eagles have structures on their toes called spicules that allow them to grasp fish.Ospreys also have this adaptation.[55] Bird prey may occasionally be attacked in flight, with prey up to the size ofCanada geese attacked and killed in mid-air.[62] It has been estimated that the bald eagle's grip (measured as newtons per square meter, or pounds per square inch) is ten times stronger than that of a human.[63] Bald eagles can fly with fish at least equal to their own weight, but if the fish is too heavy to lift, the eagle may be dragged into the water. Bald eagles can swim, but in some cases, they drag their catch ashore with their talons. Still, some eagles drown or succumb tohypothermia.[64] Many sources claim that bald eagles, like all large eagles, cannot normally take flight carrying prey more than half of their own weight unless aided by favorable wind conditions.[47][65] On numerous occasions, when large prey such as large fish including mature salmon or geese are attacked, eagles have been seen to make contact and then drag the prey in a strenuously labored, low flight over the water to a bank, where they then finish off and dismember the prey.[32][30][59][60] When food is abundant, an eagle can gorge itself by storing up to 1 kg (2.2 lb) of food in a pouch in the throat called a crop. Gorging allows the bird to fast for several days if food becomes unavailable.[47] Occasionally, bald eagles may hunt cooperatively when confronting prey, especially relatively large prey such as jackrabbits or herons, with one bird distracting potential prey, while the other comes behind it in order to ambush it.[16][66][67] While hunting waterfowl, bald eagles repeatedly fly at a target and cause it to dive repeatedly, hoping to exhaust the victim so it can be caught (white-tailed eagles have been recorded hunting waterfowl in the same way). When hunting concentrated prey, a successful catch often results in the hunting eagle being pursued by other eagles and needing to find an isolated perch for consumption if it is able to carry it away successfully.[32]
They obtain much of their food ascarrion or via a practice known askleptoparasitism, by which they steal prey away from other predators. Due to their dietary habits, bald eagles are frequently viewed in a negative light by humans.[19] Thanks to their superior foraging ability and experience, adults are generally more likely to hunt live prey than immature eagles, which often obtain their food from scavenging.[68][69] They are not very selective about the condition or origin, whether provided by humans, other animals, auto accidents or natural causes, of a carcass's presence, but will avoid eating carrion where disturbances from humans are a regular occurrence. They will scavenge carcasses up to the size ofwhales, though carcasses ofungulates and large fish are seemingly preferred.[32] Congregated wintering waterfowl are frequently exploited for carcasses to scavenge by immature eagles in harsh winter weather.[70] Bald eagles also may sometimes feed on material scavenged or stolen fromcampsites andpicnics, as well asgarbage dumps (dump usage is habitual mainly inAlaska)[71] and fish-processing plants.[72]
InSoutheast Alaska, fish comprise approximately 66% of the year-round diet of bald eagles and 78% of the prey brought to the nest by the parents.[74] Eagles living in theColumbia River Estuary inOregon were found to rely on fish for 90% of their dietary intake.[75] At least 100 species of fish have been recorded in the bald eagle's diet.[60] From observation in theColumbia River, 58% of the fish were caught alive by the eagle, 24% were scavenged as carcasses and 18% were pirated away from other animals.[75]
Fish taken by bald eagles varies in size, but bald eagles take larger fish than other piscivorous birds inNorth America, typically range from 20 to 75 cm (7.9 to 29.5 in) and prefer 36 cm (14 in) fish.[86] When experimenters offered fish of different sizes in the breeding season aroundLake Britton inCalifornia, fish measuring 34 to 38 cm (13 to 15 in) were taken 71.8% of the time by parent eagles while fish measuring 23 to 27.5 cm (9.1 to 10.8 in) were chosen only 25% of the time.[87] At nests aroundLake Superior, the remains of fish (mostlysuckers) were found to average 35.4 cm (13.9 in) in total length.[88] In the Columbia River Estuary, most preyed on by eagles were estimated to measure less than 30 cm (12 in), but larger fish between 30 and 60 cm (12 and 24 in) or even exceeding 60 cm (24 in) in length also taken especially during the non-breeding seasons.[75] They can take fish up to at least twice their own weight, such as large mature salmons,carps, or evenmuskellunge (Esox masquinongy), by dragging its catch with talons and pull toward ashore.[30][59][89][90] Much larger marine fish such asPacific halibut (Hippoglossus stenolepis) andlemon sharks (Negaprion brevirostris) have been recorded among bald eagle prey though probably are only taken as young, as small, newly mature fish, or as carrion.[61][91]
Benthic fishes such as catfish are usually consumed after they die and float to the surface, though while temporarily swimming in the open may be more vulnerable to predation than most fish since their eyes focus downwards.[79] Bald eagles also regularly exploit water turbines which produce battered, stunned or dead fish easily consumed.[92] Predators who leave behind scraps of dead fish that they kill, such asbrown bears (Ursus arctos),gray wolves (Canis lupus) andRed foxes (Vulpes vulpes), may be habitually followed in order to scavenge the kills secondarily.[74] Once North Pacific salmon die off after spawning, usually local bald eagles eat salmon carcasses almost exclusively. Eagles inWashington need to consume 489 g (1.078 lb) of fish each day for survival, with adults generally consuming more than juveniles and thus reducing potential energy deficiency and increasing survival duringwinter.[93]
Behind fish, the next most significant prey base for bald eagles are otherwaterbirds. The contribution of such birds to the eagle's diet is variable, depending on the quantity and availability of fish near the water's surface. Waterbirds can seasonally comprise from 7% to 80% of the prey selection for eagles in certain localities.[75][94] Overall, birds are the most diverse group in the bald eagle's prey spectrum, with 200 prey species recorded.[30][60][61]
Bird species most preferred as prey by eagles tend to be medium-sized, such aswestern grebes (Aechmophorus occidentalis),mallards (Anas platyrhynchos), andAmerican coots (Fulica americana) as such prey is relatively easy for the much larger eagles to catch and fly with.[19][75] American herring gull (Larus smithsonianus) are the favored avian prey species for eagles living around Lake Superior.[88]Black ducks (Anas rubripes),common eiders (Somateria mollissima), anddouble-crested cormorants (Phalacrocorax auritus) are also frequently taken in coastal Maine[81] andvelvet scoter (Melanitta fusca) was dominant prey inSan Miguel Island.[95]
Due to easy accessibility and lack of formidable nest defense against eagles by such species, bald eagles are capable of preying on such seabirds at all ages, from eggs to mature adults, and they can effectively cull large portions of a colony.[96] Along some portions of the North Pacific coastline, bald eagles which had historically preyed mainlykelp-dwelling fish and supplementallysea otter (Enhydra lutris) pups are now preying mainly on seabird colonies since both the fish (possibly due to overfishing) and otters (cause unknown) have had steep population declines, causing concern for seabird conservation.[97] Because of this more extensive predation, some biologist has expressed concern thatmurres are heading for a "conservation collision" due to heavy eagle predation.[96] Eagles have been confirmed to attack nocturnally active, burrow-nesting seabird species such asstorm petrels andshearwaters by digging out their burrows and feeding on all animals they find inside.[98] If a bald eagle flies close by, waterbirds will often fly away en masse, though they may seemingly ignore a perched eagle in other cases. When the birds fly away from a colony, this exposes their unprotected eggs and nestlings to scavengers such asgulls.[96]
While they usually target small to medium-sized seabirds, larger seabirds such asgreat black-backed gulls (Larus marinus) andnorthern gannets (Morus bassanus) andbrown pelicans (Pelecanus occidentalis) of all ages can successfully be taken by bald eagles.[99][100][101] Similarly, large waterbirds are occasionally killed. Geese such as winteringemperor geese (Chen canagica) andsnow geese (C. caerulescens), which gather in large groups, sometimes becoming regular prey.[32][65] SmallerRoss's geese (Anser rossii) are also taken, as well as large-sizedCanada geese (Branta canadensis).[102][79] Predation on the largest subspecies (Branta canadensis maxima) has been reported.[103] Other large waterbird prey includecommon loons (Gavia immer) of all ages.[104] Large wading birds can also fall prey to bald eagles. For thegreat blue herons (Ardea herodias), bald eagles are their only serious enemies of all ages.[59][105] Slightly largerSandhill cranes (Grus canadensis) can be taken as well.[106] While adultwhooping cranes (Grus americana) are too large and formidable, their chicks can fall prey to bald eagles.[107][108][109] They even occasionally prey on adulttundra swans (Cygnus columbianus).[110] Youngtrumpeter swans (Cygnus buccinator) are also taken, and an unsuccessful attack on an adult swan has been photographed.[111][112]
Bald eagles have been occasionally recorded as killing otherraptors. In some cases, these may be attacks of competition orkleptoparasitism on rival species but end with the consumption of the dead victims. Nine species of otheraccipitrids andowls are known to have been preyed upon by bald eagles. Owl prey species have ranged in size fromwestern screech owls (Megascops kennicotti) tosnowy owls (Bubo scandiacus).[30][60][61][113] Larger diurnal raptors known to have fallen victim to bald eagles have includedred-tailed hawks (Buteo jamaicensis),[114]peregrine falcons (Falco peregrinus),[115]northern goshawks (Accipiter gentilis),[116] ospreys (Pandion haliaetus)[117] andblack (Coragyps atratus) andturkey vultures (Cathartes aura).[118]
Mammalian preys are generally less frequently taken than fish or avian prey. However, in some regions, such as landlocked areas of North America, wintering bald eagles may become habitual predators of medium-sized mammals that occur in colonies or local concentrations, such asprairie dogs (Cynomys sp.) andjackrabbits (Lepus sp.).[19][119] Bald eagles inSeedskadee National Wildlife Refuge often hunt in pair to catch cottontails, jackrabbits and prairie dogs.[120] They can attack and prey onrabbits and hares of nearly any size, frommarsh rabbits (Sylvilagus palustris) toblack andwhite-tailed jackrabbits (Lepus californicus &L. townsendii), andArctic hares (Lepus arcticus).[121][122][85] In theSan Luis Valley, white-tailed jackrabbits can be important prey.[110] Additionally, rodents such asmontane voles (Microtus montanus),brown rats (Rattus norvegicus), and varioussquirrels are taken as supplementary prey.[122][15][81] Larger rodents such asmuskrats (Ondatra zibethicus), young or small adultnutrias (Myocastor coypus) andgroundhogs (Marmota monax) are also preyed upon.[123][124] EvenNorth American porcupines (Erethizon dorsatum) are reportedly attacked and killed.[125]
Where available,seal colonies can provide a lot of food. OnProtection Island, Washington, they commonly feed onharbor seal (Phoca vitulina) afterbirths, still-borns and sickly seal pups.[126] Similarly, bald eagles in Alaska readily prey on sea otter (Enhydra lutris) pups.[127] Small to medium-sized terrestrial mammalian carnivores can be taken infrequently.Mustelid includingAmerican martens (Martes pennanti),[128]American minks (Neogale vison),[129] and largerfisher cats (Pekania pennanti) are known to be hunted.[130]Foxes are also taken, includingisland foxes ( Urocyon littoralis),[131]Arctic foxes (Vulpes lagopus),[132] andgrey foxes (Urocyon cinereoargenteus).[133] Although fox farmers claimed that bald eagle heavily prey on young and adult free-range Arctic fox, the predation events are sporadic.[134][135] In one instance, two bald eagles fed upon ared fox (Vulpes vulpes) that had tried to cross a frozen Delaware Lake inOhio.[136] Other medium-sized carnivorans such asstriped skunks (Mephitis mephitis),[137]American hog-nosed skunks (Conepatus leuconotus),[138] andcommon raccoons (Procyon lotor)[133] are taken, as well asdomestic cats (Felis catus) anddogs (Canis familiaris).[139][134]
Other wild mammalian prey include fawns ofdeer such aswhite-tailed deer (Odocoileus virginianus) andSitka deer (Odocoileus hemionus sitkensis), which weigh around 3 kg (6.6 lb) can be taken alive by bald eagles.[140][141] In one instance, a bald eagle was observed carrying 6.8 kg (15 lb)mule deer (Odocoileus hemionus) fawn.[142] Additionally,Virginia opossums (Didelphis virginiana) can be preyed upon. Still, predation events are rare due to their nocturnal habits.[121][143][133]
Together with thegolden eagle, bald eagles are occasionally accused of preying on livestock, especiallysheep (Ovis aries). There are a handful of proven cases of lamb predation, some specimens weighing up to 11 kg (24 lb), by bald eagles. Still, they are much less likely to attack a healthy lamb than a golden eagle. Both species prefer native, wild prey and are unlikely to cause any extensive detriment to human livelihoods.[144] There is one case of a bald eagle killing and feeding on an adult, pregnant ewe (then joined in eating the kill by at least three other eagles), which, weighing on average over 60 kg (130 lb), is much larger than any other known prey taken by this species.[145]
When competing for food, eagles will usually dominate other fish-eaters and scavengers, aggressively displacing mammals such ascoyotes (Canis latrans) and foxes, and birds such ascorvids, gulls,vultures and other raptors.[71] Occasionally, coyotes,bobcats (Lynx rufus) and domestic dogs (Canis familiaris) can displace eagles from carrion, usually less confident immature birds, as has been recorded in Maine.[153] Bald eagles are less active, bold predators than golden eagles and get relatively more of their food as carrion and from kleptoparasitism (although it is now generally thought that golden eagles eat more carrion than was previously assumed).[95][20] However, the two species are roughly equal in size, aggressiveness and physical strength and so competitions can go either way. Neither species is known to be dominant, and the outcome depends on the size and disposition of the individual eagles involved.[32] Wintering bald and golden eagles inUtah both sometimes won conflicts, though in one recorded instance a single bald eagle successfully displaced two consecutive golden eagles from a kill.[154]
Though bald eagles face few natural threats, an unusual attacker comes in the form of thecommon loon (G. immer), which is also taken by eagles as prey. While common loons normally avoid conflict, they are highly territorial and will attack predators and competitors by stabbing at them with their knife-like bill; as the range of the bald eagle has increased following conservation efforts, these interactions have been observed on several occasions, including a fatality of a bald eagle in Maine that is presumed to have come about as a result of it attacking a nest, then having a fatalpuncture wound inflicted by one or both loon parents.[155]
The bald eagle is thought to be much more numerous in North America than the golden eagle, with the bald species estimated to number at least 150,000 individuals, about twice as many as there are golden eagles estimated to live in North America.[20][38] Due to this, bald eagles often outnumber golden eagles at attractive food sources.[20] Despite the potential for contention between these animals, in New Jersey during winter, a golden eagle and numerous bald eagles were observed to huntsnow geese alongside each other without conflict. Similarly, both eagle species have been recorded, via video-monitoring, to feed on gut piles and carcasses of white-tailed deer (Odocoileus virginianus) in remote forest clearings in the easternAppalachian Mountains without apparent conflict.[20] Bald eagles are frequently mobbed by smaller raptors, due to their infrequent but unpredictable tendency to hunt other birds of prey.[154] Many bald eagles are habitual kleptoparasites, especially in winters when fish are harder to come by. They have been recorded stealing fish from other predators such as ospreys,herons and evenotters.[32][156] They have also been recorded opportunistically pirating birds from peregrine falcons (Falco peregrinus), prairie dogs fromferruginous hawks (Buteo regalis) and even jackrabbits from golden eagles.[157][158] When they approach scavengers such as dogs, gulls or vultures at carrion sites, they often attack them in an attempt to force them to disgorge their food.[47] Healthy adult bald eagles are not preyed upon in the wild and are thus consideredapex predators.[159]
Reproduction
Bald eagles are sexually mature at four or five years of age. When they are old enough to breed, they often return to the area where they were born. Bald eagles have high mate fidelity and generallymate for life. However, if one pair member dies or disappears, the survivor will choose a new mate. A pair that has repeatedly failed in breeding attempts may split and look for new mates.[160] Bald eaglecourtship involves elaborate, spectacular calls and flight displays by the males.
Bald eagles with talons locked together in amating dance spiral free-fall dive
The flight includes swoops, chases, and cartwheels, in which they fly high, lock talons, and free-fall, separating just before hitting the ground.[59][161][162] Usually, a territory defended by a mature pair will be 1 to 2 km (0.62 to 1.24 mi) of waterside habitat.[19]
Compared to most other raptors, which mostly nest in April or May, bald eagles are early breeders: nest building or reinforcing is often by mid-February, egg laying is often late February (sometimes during deep snow in the North), and incubation is usually mid-March and early May. Eggs hatch from mid-April to early May, and the young fledge from late June to early July.[19] Thenest is the largest of any bird inNorth America; it is used repeatedly over many years and with new material added each year may eventually be as large as 4 m (13 ft) deep, 2.5 m (8.2 ft) across and weigh 1metric ton (1.1short tons).[11] One nest inFlorida was found to be 6.1 m (20 ft) deep, 2.9 meters (9.5 ft) across, and to weigh 3 short tons (2.7 metric tons).[163] This nest is on record as the largest tree nest ever recorded for any animal.[164] Usually nests are used for under five years, as they either collapse in storms or break the branches supporting them by their sheer weight. However, one nest in theMidwest was occupied continuously for at least 34 years.[47] The nest is built ofbranches, usually in large trees found near water. When breeding where there are no trees, the bald eagle will nest on the ground, as has been recorded largely in areas largely isolated from terrestrial predators, such asAmchitka Island inAlaska.[71]
InSonora, Mexico, eagles have been observed nesting on top of hecho cactuses (Pachycereus pectin-aboriginum).[165] Nests located on cliffs and rock pinnacles have been reported historically inCalifornia,Kansas,Nevada,New Mexico andUtah, but currently are only verified to occur only in Alaska andArizona.[19] Theeggs average about 73 mm (2.9 in) long, ranging from 58 to 85 mm (2.3 to 3.3 in), and have a breadth of 54 mm (2.1 in), ranging from 47 to 63 mm (1.9 to 2.5 in).[55][59] Eggs in Alaska averaged 130 g (4.6 oz) in mass, while inSaskatchewan they averaged 114.4 g (4.04 oz).[166][167] As with their ultimate body size, egg size tends to increase with distance from the equator.[59] Eagles produce between one and three eggs per year, two being typical. Rarely, four eggs have been found in nests, but these may be exceptional cases ofpolygyny.[134] Eagles in captivity have been capable of producing up to seven eggs.[168] It is rare for all three chicks to successfully reach the fledgling stage. The oldest chick often bears the advantage of a larger size and louder voice, which tends to draw the parents' attention towards it.[19] Occasionally, as is recorded in many large raptorial birds, the oldest sibling sometimes attacks and kills its younger sibling(s), especially early in the nesting period when their sizes are most different.[19] However, nearly half of the known bald eagles produce two fledglings (more rarely three), unlike in some other "eagle" species such as some in the genusAquila, in which a second fledgling is typically observed in less than 20% of nests, despite two eggs typically being laid.[29] Both the male and female take turns incubating the eggs, but the female does most of the sitting. The parent not incubating will hunt for food or look for nesting material during this stage. For the first two to three weeks of the nestling period, at least one adult is at the nest almost 100% of the time. After five to six weeks, the attendance of parents usually drops off considerably (with the parents often perching in trees nearby).[19]
A young eaglet can gain up to 170 g (6.0 oz) a day, the fastest growth rate of any North American bird.[47] The young eaglets pick up and manipulate sticks, play tug of war with each other, practice holding things in their talons, and stretch and flap their wings. By eight weeks, the eaglets are strong enough to flap their wings, lift their feet off the nest platform, and rise in the air.[47] The young fledge at anywhere from 8 to 14 weeks of age, though will remain close to the nest and be attended to by their parents for a further six weeks. Juvenile eagles first start dispersing away from their parents about eight weeks after they fledge. Variability in departure date related to effects of sex and hatching order on growth and development.[167] For the next four years, immature eagles wander widely in search of food until they attain adult plumage and are eligible to reproduce.[169]
Male eagles have been observed killing andcannibalizing their chicks.[170] In 2024, at the National Conservation Training Center (NCTC) inWest Virginia, the NCTC's Eagle Cam recorded two bald eagle chicks being attacked and devoured by their father as soon as the mother departed from the nest. The NCTC noted in its statement on the incident that such behavior "has been observed in other nests and is not uncommon in birds of prey."[171]
On rare occasions, bald eagles have been recorded to adopt other raptor fledglings into their nests, as seen in 2017 by a pair of eagles in Shoal Harbor Migratory Bird Sanctuary nearSidney, British Columbia. The pair of eagles in question are believed to have carried a juvenilered-tailed hawk back to their nest, presumably as prey, whereupon the chick was accepted into the family by both the parents and the eagles' three nestlings.[172] The hawk, nicknamed "Spunky" by biologists monitoring the nest, fledged successfully.[173]
Longevity and mortality
Newly fledged juvenile
The average lifespan of bald eagles in the wild is around 20 years, with the oldest confirmed one having been 38 years of age.[174] In captivity, they often live somewhat longer. In one instance, a captive individual inNew York lived for nearly 50 years.[175] As with size, the average lifespan of an eagle population appears to be influenced by its location and access to prey.[176] As they are no longer heavily persecuted, adult mortality is quite low. In one study ofFlorida eagles, adult bald eagles reportedly had 100% annual survival rate.[20] InPrince William Sound, Alaska, adults had an annual survival rate of 88% even after theExxon Valdez oil spill adversely affected eagles in the area.[177] Of 1,428 individuals from across the range necropsied by theNational Wildlife Health Center from 1963 to 1984, 329 (23%) eagles died from trauma, primarily impact with wires and vehicles; 309 (22%) died from gunshot; 158 (11%) died from poisoning; 130 (9%) died from electrocution; 68 (5%) died from trapping; 110 (8%) from emaciation; and 31 (2%) from disease; cause of death was undetermined in 293 (20%) of cases.[178] In this study, 68% of mortality was human-caused.[178] Today, eagle-shooting is believed to be considerably reduced due to the species' protected status.[179] AU.S. Fish and Wildlife Service study of 1,490 bald eagle deaths from 1986 through 2017 inMichigan found that 532 (36%) died due to being struck by cars while scavengingroadkill and 176 (12%) died due tolead poisoning from ingesting fragments oflead ammo andfishing gear present incarrion, with the proportion of both causes of death increasing significantly towards the end of the study period.[180][181]
Most non-human-related mortality involves nestlings or eggs. Around 50% of eagles survive their first year.[169] However, in theChesapeake Bay area, 100% of 39 radio-tagged nestlings survived to their first year.[182] Nestling or egg fatalities may be due to nest collapses, starvation, sibling aggression or inclement weather. Another significant cause of egg and nestling mortality is predation. Nest predators include largegulls,corvids (includingravens,crows andmagpies),wolverines (Gulo gulo),fishers (Pekania pennanti),red-tailed hawks,owls, othereagles,bobcats,American black bears (Ursus americanus) andraccoons.[166][183][184][185][110][186][187][188] If food access is low, parental attendance at the nest may be lower because both parents may have to forage, thus resulting in less protection.[29] Nestlings are usually exempt from predation by terrestrial carnivores that are poor tree-climbers, butArctic foxes (Vulpes lagopus) occasionally snatched nestlings from ground nests onAmchitka Island inAlaska before they were extirpated from the island.[71] The bald eagle will defend its nest fiercely from all comers and has even repelled attacks frombears, having been recorded knocking a black bear out of a tree when the latter tried to climb a tree holding nestlings.[189]
Relationship with humans
Population decline and recovery
Inside a waste collection and transfer facility, inHomer, Alaska, United States
Once a common sight in much of the continent, the bald eagle was severely affected in the mid-20th century by a variety of factors, among them the thinning of egg shells attributed to use of the pesticideDDT.[190] Bald eagles, like manybirds of prey, were especially affected by DDT due tobiomagnification. DDT itself was not lethal to the adult bird, but it interfered with theircalcium metabolism, making them either sterile or unable to lay healthyeggs; many of their eggs were too brittle to withstand the weight of a brooding adult, making it nearly impossible for them to hatch.[36] It is estimated that in the early 18th century the bald eagle population was 300,000–500,000,[191] but by the 1950s there were only 412 nesting pairs in the 48contiguous states of the U.S.[192][193]Other factors in bald eagle population reductions were a widespread loss of suitable habitat, as well as both legal and illegal shooting. In 1930 aNew York City ornithologist wrote that in the territory ofAlaska in the previous 12 years, approximately 70,000 bald eagles had been shot. Many of the hunters killed the bald eagles under the long-held beliefs that bald eagles grabbed younglambs and even children with their talons, yet the birds were innocent of most of these alleged acts of predation (lamb predation is rare, human predation is thought to be non-existent).[194] Illegal shooting was described as "the leading cause of direct mortality in both adult and immature bald eagles" by theU.S. Fish and Wildlife Service in 1978.[195] Leading causes of death in bald eagles includelead pollution,poisoning,collision with motor vehicles, andpower lineelectrocution.[196] A study published in 2022 in the Journal Science found that more than half of adult eagles across 38 U.S. states suffered from lead poisoning.[197] The primary cause is when eagles scavenge carcasses of animals shot by hunters.[197] These are often tainted withlead shotgun pellets,rifle rounds, orfishing tackle.[197][181]
The species was first protected in theU.S. andCanada by the1918 Migratory Bird Treaty, later extended to all ofNorth America. TheBald and Golden Eagle Protection Act, approved by theU.S. Congress in 1940, protected the bald eagle and thegolden eagle, prohibiting commercial trapping and killing of the birds as well as collecting their eggs.[198] The bald eagle was declared an endangered species in the U.S. in 1967, and amendments to the 1940 act between 1962 and 1972 further restricted commercial uses and increased penalties for violators.[199][200] Perhaps most significant in the species' recovery, in 1972, DDT was banned from usage in the United States due to the fact that it inhibited the reproduction of many birds.[201] DDT was completely banned in Canada in 1989, though its use had been highly restricted since the late 1970s.[202]
First-year juvenile bald eagle atAnacortes, Washington, United States
With regulations in place and DDT banned, the eagle population rebounded. The bald eagle can be found in growing concentrations throughout the United States and Canada, particularly near large bodies of water. In the early 1980s, the estimated total population was 100,000 individuals, with 110,000–115,000 by 1992;[11] the U.S. state with the largest resident population is Alaska, with about 40,000–50,000, with the next highest population theCanadian province ofBritish Columbia with 20,000–30,000 in 1992.[11] Obtaining a precise count of the bald eagle population is extremely difficult. The most recent data submitted by individual states was in 2006, when 9789 breeding pairs were reported.[203] For some time, the stronghold breeding population of bald eagles in thelower 48 states was inFlorida, where over a thousand pairs have held on while populations in other states were significantly reduced by DDT use. Today, the contiguous state with the largest number of breeding pairs of eagles isMinnesota, with an estimated 1,312 pairs, surpassing Florida's most recent count of 1,166 pairs. 23, or nearly half, of the 48 contiguous states now have at least 100 breeding pairs of bald eagles.[38] InWashington State, there were only 105 occupied nests in 1980. That number increased by about 30 per year, so that by 2005 there were 840 occupied nests. 2005 was the last year that theWashington Department of Fish and Wildlife counted occupied nests. Further population increases in Washington may be limited by the availability of late winter food, particularlysalmon.[204]
The bald eagle was officially removed from theU.S. federal government's list of endangered species on July 12, 1995, by the U.S. Fish & Wildlife Service, when it was reclassified from "endangered" to "threatened". On July 6, 1999, a proposal was initiated "To Remove the Bald Eagle in the Lower 48 States From the List of Endangered and Threatened Wildlife". It was de-listed on June 28, 2007.[205] It has also been assigned a risk level of "least-concern" category on theIUCN Red List.[2] In theExxon Valdez oil spill of 1989, an estimated 247 were killed inPrince William Sound, though the local population returned to its pre-spill level by 1995.[16] In some areas, the increase in eagles has led to decreases in other bird populations[206] and the eagles may be considered apest.[207]
Killing permits
In December 2016, the U.S. Fish and Wildlife Service proposed extending the permits issued to wind generation companies to allow them to kill up to 4,200 bald eagles per year without facing a penalty, four times the previous number. The permits would last 30 years, six times the previous five-year term.[208][209]
Permits are required to keep bald eagles in captivity in the United States. Permits are primarily issued to public educational institutions, and the eagles that they show are permanently injured individuals that cannot be released to the wild. The facilities where eagles are kept must be equipped with adequate caging, as well as workers experienced in the handling and care of eagles.[210] The bald eagle can be long-lived in captivity if well cared for, but does not breed well even under the best conditions.[211]
In Canada[212] andEngland,[213] a license is required to keep bald eagles forfalconry.[214] Bald eagles cannot legally be kept for falconry in the United States, but a license may be issued in some jurisdictions to allow use of such eagles in birds-of-prey flight shows.[215][216]
The bald eagle is a sacred bird in someNorth American cultures, and itsfeathers, like those of thegolden eagle, are central to many religious andspiritual customs among Native Americans. Eagles are considered spiritual messengers between gods and humans by some cultures.[218] Manypowwow dancers use the eagleclaw as part of their regalia as well. Eagle feathers are often used in traditional ceremonies, particularly in the construction of regalia worn and as a part of fans, bustles and head dresses. In theNavajo tradition an eagle feather is represented to be a protector, along with the feather Navajo medicine men use the leg and wing bones for ceremonial whistles.[219] TheLakota, for instance, give an eagle feather as a symbol of honor to person who achieves a task. In modern times, it may be given on an event such as a graduation from college.[220] ThePawnee consider eagles as symbols of fertility because their nests are built high off the ground and because they fiercely protect their young.[221] TheChoctaw consider the bald eagle, who has direct contact with the upper world of the sun, as a symbol of peace.[222]
During theSun Dance, which is practiced by manyPlains Indian tribes, the eagle is represented in several ways. The eagle nest is represented by the fork of the lodge where the dance is held. A whistle made from the wing bone of an eagle is used during the course of the dance. Also during the dance, amedicine man may direct his fan, which is made of eagle feathers, to people who seek to be healed. The medicine man touches the fan to the center pole and then to the patient, in order to transmit power from the pole to the patient. The fan is then held up toward the sky, so that the eagle may carry the prayers for the sick to the Creator.[223]
Eagle feather law stipulates that only individuals of certifiable Native American ancestry enrolled in a federally recognized tribe are legally authorized to obtain or possess bald or golden eagle feathers for religious or spiritual use. The constitutionality of these laws has been questioned by Native American groups on the basis that it violates theFirst Amendment by affecting ability to practice their religion freely.[224][225]
TheNational Eagle Repository, a division of theFWS, exists as a means to receive, process, and store bald and golden eagles which are found dead and to distribute the eagles, their parts and feathers tofederally recognized Native American tribes for use in religious ceremonies.[226]
The bald eagle is the national symbol of the United States.[227] It was adopted as a national emblem in 1782. It has long been considered the "national bird", though unofficially until anact of Congress in December 2024.[228][229]
The bald eagle appears on most official seals of the U.S. government, including thepresidential seal, thepresidential flag, and in the logos of many U.S. federal agencies. Between 1916 and 1945, the presidential flag (but not the seal) showed an eagle facing to its left (the viewer's right), which gave rise to theurban legend that the flag is changed to have the eagle face towards the olive branch in peace, and towards the arrows in wartime.[233]
Contrary to popular legend, there is no evidence thatBenjamin Franklin ever publicly supported thewild turkey (Meleagris gallopavo), rather than the bald eagle, as a symbol of the United States. However, in a letter written to his daughter in 1784 from Paris, criticizing theSociety of the Cincinnati, he stated his personal distaste for the bald eagle's behavior. In the letter Franklin states:[234]
For my own part. I wish the bald eagle had not been chosen the representative of our country. He is a bird of bad moral character. He does not get his living honestly ... besides he is a rank coward: The littleking bird not bigger than a sparrow attacks him boldly and drives him out of the district.
Franklin opposed the creation of the Society because he viewed it, with its hereditary membership, as anoble order unwelcome in the newly independent Republic, contrary to the ideals ofLucius Quinctius Cincinnatus, for whom the Society was named. His reference to the two kinds of birds is interpreted as a satirical comparison between the Society of the Cincinnati and Cincinnatus.[235]
Popular culture
Largely because of its role as a symbol of the United States, but also because it is a large predator, the bald eagle is often represented in popular culture. In film and television, the call of thered-tailed hawk is often substituted for the bald eagle's because the former is much louder and more powerful.[236]
^Dietz, Joshua."What's in a Name". Smithsonian National Zoological Park. Archived fromthe original on August 5, 2007. RetrievedAugust 19, 2007.
^Linnaeus, Carolus (1766).Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata (in Latin). Holmiae. (Laurentii Salvii).
^Dunning, Jr., J.B., ed. (1993).CRC Handbook of Avian Body Masses. CRC Press, Ann Arbor.
^Murphy, T. & Hope, C."Bald Eagles in South Carolina"(PDF). Department of Natural Resources of South Carolina.Archived(PDF) from the original on October 9, 2022. RetrievedJanuary 4, 2013.
^Maehr, D. S.; Kale, H. W. (2005).Florida's Birds: A Field Guide and Reference. Pineapple Press Inc.
^Patterson, D.A.; McClelland, B.R.; Shea, D.S.; McClelland, P.T. (1998). "Size Variation of Migrant Bald Eagles at Glacier National Park, Montana".J. Raptor Res.32 (2):120–25.
^Zylo, M. T. (2012).Bald eagles (Haliaeetus leucocephalus) wintering in northern Arizona select perches based on food availability, visibility and cover (MS thesis). Northern Arizona University.ISBN978-1-267-58789-3.ProQuest1039149407.
^abcdefghPalmer, R. S., ed. (1988).Handbook of North American Birds Volume VI: Diurnal Raptors (Part 1). Yale University Press.
^Gende, S. M. (2008). "Perspectives on the Breeding Biology of Bald Eagles in Southeast Alaska". In Wright, Bruce A.; Schempf, Phil (eds.).Bald Eagles in Alaska. University of Alaska Southeast.
^Andrew, J. M.; Mosher, J. A. (1982). "Bald Eagle nest site selection and nesting habitat in Maryland".Journal of Wildlife Management.46 (2):382–90.doi:10.2307/3808650.JSTOR3808650.
^Wood, P. B.; Edwards, T. C.; Collopy, M. W. (1989). "Characteristics of Bald Eagle nesting habitat in Florida".Journal of Wildlife Management.53 (2):441–449.doi:10.2307/3801148.JSTOR3801148.
^Swenson, J. E.; Alt, K. L.; Eng, R. L. (1986). "Ecology of Bald Eagles in the greater Yellowstone ecosystem".Wildlife Monographs.95 (95):3–46.JSTOR3830668.
^abcdefghStalmaster, M.V. (1987).The Bald Eagle. New York: Universe Books.
^abcdeSherrod, S. K. (1978). "Diets of North American Falconiformes".Raptor Res.12 (3/4):49–121.
^abcdCollins, P. W.; Guthrie, D. A.; Rick, T. C.; Erlandson, J. M. (2005). "Analysis of prey remains excavated from an historic bald eagle nest site on San Miguel Island, California".Proceedings of the Sixth California Islands Symposium. Arcata, CA: Institute for Wildlife Studies:103–120.
^Griffin, C. R.; Baskett, T. S.; Sparrowe, R. D. (1982).Ecology of Bald Eagles wintering near a waterfowl concentration. Special Scientific Report - Wildlife. Vol. 247. Washington, D.C.: U.S. Fish and Wildlife Service.
^abcdSherrod, S. K.; White, C. M.; Williamson, F. S. L. (1976). "Biology of the Bald Eagle on Amchitka Island, Alaska".Living Bird.15:145–82.
^Dunstan, Thomas C.; Harper, James F. (1975). "Food Habits of Bald Eagles in North-Central Minnesota".The Journal of Wildlife Management.39 (1):140–143.doi:10.2307/3800476.JSTOR3800476.
^abKozie, K. D.; Anderson, R. K. (1991). "Productivity, diet, and environmental contaminants in Bald Eagles nesting near the Wisconsin shoreline of Lake Superior".Archives of Environmental Contamination and Toxicology.20 (1):41–48.Bibcode:1991ArECT..20...41K.doi:10.1007/BF01065326.PMID1996910.S2CID28781482.
^Brisbin, I. Lehr Jr.; Mowbray, Thomas B.; Poole, A.; Gill, F. (2002). "American Coot (Fulica americana)".The Birds of North America Online.doi:10.2173/bna.697a.ISSN1061-5466.
^abcdErlandson, Jon M.; et al. (2007). "Archaeological implications of a bald eagle nesting site at Ferrelo Point, San Miguel Island, California".Journal of Archaeological Science.34 (2):255–271.Bibcode:2007JArSc..34..255E.doi:10.1016/j.jas.2006.05.002.
^Mowbray, Thomas B. "Northern Gannet — Behavior". Birds of North America Online. The Cornell Lab of Ornithology. Retrieved October 17, 2011
^Shields, M. (2020). Brown Pelican (Pelecanus occidentalis), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.https://doi.org/10.2173/bow.brnpel.01
^Windels, S. K., Beever, E. A., Paruk, J. D., Brinkman, A. R., Fox, J. E., Macnulty, C. C., ... & Osborne, D. C. (2013). Effects of water‐level management on nesting success of common loons. The Journal of wildlife management, 77(8), 1626–1638.
^Forbes, L. Scott (1987). "Predation on Adult Great Blue Herons: Is It Important?".Colonial Waterbirds.10 (1):120–122.doi:10.2307/1521242.JSTOR1521242.
^Evans, R. M. and F. L. Knopf. (1993). "American White Pelican (Pelecanus erythrorhynchos)". In: A. Poole and F. Gill, (eds.),The Birds of North America, No. 57. Philadelphia: The Academy of Natural Sciences; Washington D.C.: The American Ornithologists Union.
^Rabbe, Matthew R.; Caven, Andrew J.; Wiese, Joshua D. (2019). "First description of a Bald Eagle (Haliaeetus leucocephalus) attempting depredation on an adult Whooping Crane (Grus americana) of the Aransas-Wood Buffalo population".Monographs of the Western North American Naturalist.11 (1):24–32.
^Corace III, R. Gregory; McCormick, Damon L.; Cavalieri, Vincent (2006). "Population growth parameters of a reintroduced trumpeter swan flock, Seney National Wildlife Refuge, Michigan, USA (1991-2004)".Waterbirds.29 (1):38–42.doi:10.1675/1524-4695(2006)29[38:PGPOAR]2.0.CO;2.S2CID86088372.
^Jackman, R. E.; Hunt, W. G.; Jenkins, J. M.; Detrich, P. J. (1999). "Prey of nesting bald eagles in northern California".Journal of Raptor Research.33 (2):87–96.
^Anthony, R. G.; Estes, J. A.; Ricca, M. A.; Miles, A. K.; Forsman, E. D. (2008). "Bald eagles and sea otters in the Aleutian archipelago: indirect effects of trophic cascades".Ecology.89 (10):2725–2735.Bibcode:2008Ecol...89.2725A.doi:10.1890/07-1818.1.PMID18959310.
^Cartron, J. L. E., ed. (2010). "Chapter 11: Northern Goshawk".Raptors of New Mexico. UNM Press.ISBN978-0-8263-4145-7.
^abcMcEwan, Linda C.; Hirth, David H. (1980). "Food habits of the Bald Eagle in north-central Florida".The Condor.82 (2):229–231.doi:10.2307/1367485.JSTOR1367485.
^abKralovec, Mary L.; et al. (1992). "Nesting productivity, food habits, and nest sites of bald eagles in Colorado and southeastern Wyoming".The Southwestern Naturalist.37 (4):356–361.Bibcode:1992SWNat..37..356K.doi:10.2307/3671786.JSTOR3671786.
^Watson, James W. (2002). "Comparative Home Ranges and Food Habits of Bald Eagles Nesting in Four Aquatic Habitats in Western Washington".Northwestern Naturalist.83 (3). Society for Northwestern Vertebrate Biology:101–08.doi:10.2307/3536608.JSTOR3536608.
^Erb, John; Sampson, B.; Coy, P. (2010). "Survival and causes of mortality for fisher and marten in Minnesota".Minn. Dep. Nat. Resour. Summ. Wildl. Res. Findings:24–31.
^Audet, Alexandra M.; Robbins, C. Brian; Larivière, Serge (December 26, 2002)."Alopex lagopus".Mammalian Species (713):1–10.doi:10.1644/0.713.1.
^abcOberholser, Harry Church (1906).The North American eagles and their economic relations.
^abcBent, A. C. 1937.Life histories of North American birds of prey, Part 1. U.S. National Museum Bulletin 167.
^Anthony, R. G., Estes, J. A., Ricca, M. A., Miles, A. K., & Forsman, E. D. (2008). Bald eagles and sea otters in the Aleutian archipelago: indirect effects of trophic cascades. Ecology, 89(10), 2725-2735.
^Duquette, Jared F.; et al. (2011). "Bald eagle predation of a white-tailed deer fawn".Northeastern Naturalist.18 (1):87–94.doi:10.1656/045.018.0108.S2CID85843273.
^McCollough, M. A.; Todd, C. S.; Owen R. B. Jr. (1994). "Supplemental feeding program for wintering Bald Eagles in Maine".Wildlife Society Bulletin.22 (2):147–54.doi:10.1016/0006-3207(96)83230-7.JSTOR3783240.
^abSabine, N.; Gardner, K. (1987). "Agonistic encounters between Bald Eagles and other raptors wintering in west central Utah".Journal of Raptor Research.21:118–120.
^Gilbert, S.; Tomassoni, P.; Kramer, P. A. (1981). "History of captive management and breeding of Bald Eagles".International Zoo Yearbook.21:101–09.doi:10.1111/j.1748-1090.1981.tb01959.x.
^abWood, P. B., D. A. Buehler, and M. A. Byrd. (1990). "Raptor status report – Bald Eagle". pp. 13–21 inProceedings of the southeast raptor management symposium and workshop. (Giron Pendleton, B., Ed.) National Wildlife Federation Washington, D.C.
^Fraser, J. D. (1985). "The impact of human activities on Bald Eagle populations-a review". pp. 68–84 inThe Bald Eagle in Canada. (Gerrard, J. M. and T. M. Ingram, Eds.) White Horse Plains Publishers Headingley, Manitoba.
^Buehler, D. A.; Fraser, J. D.; Seegar, J. K. D.; Therres, G. D.; Byrd, M. A. (1991). "Survival rates and population dynamics of Bald Eagles on Chesapeake Bay".Journal of Wildlife Management.55 (4):608–13.doi:10.2307/3809506.JSTOR3809506.
^Sprunt, A.; Ligas, F. J. (1964). "Excerpts from convention addresses on the 1963 Bald Eagle report".Audubon.66:45–47.
^Mckelvey, R. W.; Smith, D. W. (1979). "A black bear in a Bald Eagle nest".Murrelet.60: 106.
^Nash, C.; Pruett-Jones, M.; Allen, G. T. (1980). "The San Juan Islands Bald Eagle nesting survey". In Knight, R. L.; Allen, G. T.; Stalmaster, M. V.; Servheen, C. W. (eds.).Proceedings of Washington Bald Eagle symposium. Seattle, WA: The Nature Conservancy. pp. 105–15.
^Lovallo, M. J. (2008). "Status and management of fisher (Martes pennanti) in Pennsylvania".Management Plan Developed by Bureau of Wildlife Management. Harrisburg, USA: Pennsylvania Game Commission.
^"Adopt a Bald Eagle". Smithsonian's National Zoo & Conservation Biology Institute. May 26, 2016. Archived fromthe original on February 9, 2021. RetrievedAugust 4, 2018.
^EPA press release (December 31, 1972)."DDT Ban Takes Effect". United States Environmental Protection Agency. Archived fromthe original on July 5, 2007. RetrievedAugust 22, 2007.
^O'Brien, Greg (2005) [2002]. "Power Derived from the Outside World".Choctaws in a Revolutionary Age, 1750–1830. University of Nebraska Press. p. 58.ISBN978-0-8032-8622-1.
^Lawrence, E.A. (1990). "Symbol of a Nation: The Bald Eagle in American Culture".The Journal of American Culture.13 (1):63–69.doi:10.1111/j.1542-734X.1990.1301_63.x.
Knight, Richard L.; Gutzwiller, Kevin J. (1995).Wildlife and Recreationists: Coexistence through Management and Research. Washington, DC: Island Press.ISBN978-1-55963-257-7.OCLC30893485.
Grant, Peter J. (1988) "The Co. Kerry Bald Eagle"Twitching 1(12): 379–80 – describes plumage differences between bald eagle and white-tailed eagle in juveniles
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