The bald eagle is an opportunistic feeder which subsists mainly on fish, which it swoops down upon and snatches from the water with its talons. It builds the largest nest of any North American bird and the largest tree nests ever recorded for any animal species, up to 4m (13ft) deep, 2.5m (8.2ft) 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 in plumage, but females are about 25 percent larger than males. The yellow beak is large and hooked. The plumage of the immature is brown.
The bald eagle is the national symbol of the United States and appears on its seal. In the late 20th century it was on the brink of extirpation in the contiguous United States. Populations have since recovered, and the species' status was upgraded from "endangered" to "threatened" in 1995 and removed from the list altogether in 2007.
Taxonomy
The bald eagle is placed in the genus Haliaeetus (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 genus name is Neo-Latin: Haliaeetus (from the Ancient Greek: ἁλιάετος, romanized:haliaetos, lit.'sea eagle'),[5] and the specific name, leucocephalus, is Latinized (Ancient Greek: λευκός, romanized:leukos, lit.'white')[6] and (κεφαλή, kephalḗ, 'head').[7][8]
Bald eagle anatomy
The bald eagle was one of the many species originally described by Carl Linnaeus in his 18th-century work Systema Naturae, under the name Falco leucocephalus.[9]
H. l. leucocephalus(Linnaeus, 1766) is the nominate subspecies. It is found in the southern United States and Baja California Peninsula.[12]
H. l. washingtoniensis(Audubon, 1827), synonym H. l. alascanus Townsend, 1897, the northern subspecies, is larger than southern nominate leucocephalus. It is found in the northern United States, Canada and Alaska.[10][12]
The bald eagle forms a species pair with the white-tailed eagle of Eurasia. 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 same ecological niche in their respective ranges. The pair diverged from other sea eagles at the beginning of the Early Miocene (c. 10Ma BP) at the latest, but possibly as early as the Early/Middle Oligocene, 28 Ma BP, if the most ancient fossil record is correctly assigned to this genus.[13]
Description
Bald eagle plumage
The plumage of an adult bald eagle is evenly dark brown with a white head and tail. The tail is moderately long and slightly wedge-shaped. Males and females are identical in plumage coloration, but sexual dimorphism is evident in the species, in that females are 25% larger than males.[10] The beak, feet and irises are bright yellow. The legs are feather-free, and the toes are short and powerful with large talons. 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.[14] The beak is large and hooked, with a yellow cere.[15] The adult bald eagle is unmistakable in its native range. The closely related African 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.[16]
Head details
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.[10][14] Immature bald eagles are distinguishable from the golden eagle (Aquila chrysaetos), the only other very large, non-vulturine raptorial bird in North America, in that the former has a larger, more protruding head with a larger beak, straighter edged wings 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 its nape and (in immature birds) a highly contrasting set of white squares on the wing.[17]
The bald eagle has sometimes been considered the largest true raptor (accipitrid) in North America. The only larger species of raptor-like bird is the California condor (Gymnogyps californianus), a New World vulture which today is not generally considered a taxonomic ally of true accipitrids.[18] However, the golden eagle, averaging 4.18kg (9.2lb) and 63cm (25in) in wing chord length in its American race (Aquila chrysaetos canadensis), is merely 455g (1.003lb) lighter in mean body mass and exceeds the bald eagle in mean wing chord length by around 3cm (1.2in).[16][19] Additionally, the bald eagle's close cousins, the relatively longer-winged but shorter-tailed white-tailed eagle and the overall larger Steller's sea eagle (Haliaeetus pelagicus), may, rarely, wander to coastal Alaska from Asia.[16]
A bald eagle showing its wingspan
The bald eagle has a body length of 70–102cm (28–40in). Typical wingspan is between 1.8 and 2.3m (5ft 11in and 7ft 7in) and mass is normally between 3 and 6.3kg (6.6 and 13.9lb).[16] Females are about 25% larger than males, averaging as much as 5.6kg (12lb), and against the males' average weight of 4.1kg (9.0lb).[10][20][21][22]
The size of the bird varies by location and generally corresponds with Bergmann's rule: the species increases in size further away from the equator and the tropics. For example, eagles from South Carolina average 3.27kg (7.2lb) in mass and 1.88m (6ft 2in) in wingspan, smaller than their northern counterparts.[23] One field guide in Florida listed similarly small sizes for bald eagles there, at about 4.13kg (9.1lb).[24] Of intermediate size, 117 migrant bald eagles in Glacier National Park were found to average 4.22kg (9.3lb) but this was mostly (possibly post-dispersal) juvenile eagles, with 6 adults here averaging 4.3kg (9.5lb).[25] Wintering eagles in Arizona (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 4.74kg (10.4lb).[26]
The largest eagles are from Alaska, where large females may weigh more than 7kg (15lb) and span 2.44m (8ft 0in) across the wings.[15][27] A survey of adult weights in Alaska showed that females there weighed on average 5.35kg (11.8lb), respectively, and males weighed 4.23kg (9.3lb) against immatures which averaged 5.09kg (11.2lb) and 4.05kg (8.9lb) in the two sexes.[28][29] An Alaskan adult female eagle that was considered outsized weighed some 7.4kg (16lb).[30] R.S. Palmer listed a record from 1876 in Wyoming County, New York of an enormous adult bald eagle that was shot and reportedly scaled 8.2kg (18lb).[29] Among standard linear measurements, the wing chord is 51.5–69cm (20.3–27.2in), the tail is 23–37cm (9.1–14.6in) long, and the tarsus is 8 to 11cm (3.1 to 4.3in).[16][31] The culmen reportedly ranges from 3 to 7.5cm (1.2 to 3.0in), while the measurement from the gape to the tip of the bill is 7–9cm (2.8–3.5in).[31][32] The bill size is unusually variable: Alaskan eagles can have up to twice the bill length of birds from the southern United States (Georgia, Louisiana, Florida), with means including both sexes of 6.83cm (2.69in) and 4.12cm (1.62in) in culmen length, respectively, from these two areas.[33][34]
The call consists of weak staccato, chirping whistles, kleek kik ik ik ik, somewhat similar in cadence to a gull's call. The calls of young birds tend to be more harsh and shrill than those of adults.[16][17]
Range
Bald eagle in flight at Yellowstone National Park, Wyoming
The bald eagle's natural range covers most of North America, including most of Canada, all of the continental United States, and northern Mexico. It is the only sea eagleendemic to North America. Occupying varied habitats from the bayous of Louisiana to the Sonoran Desert and the eastern deciduous forests of Quebec and New England, northern birds are migratory, while southern birds are resident, remaining on their breeding territory all year. At minimum population, in the 1950s, it was largely restricted to Alaska, the Aleutian Islands, northern and eastern Canada, and Florida.[35] From 1966 to 2015 bald eagle numbers increased substantially throughout its winter and breeding ranges,[36] and as of 2018 the species nests in every continental state and province in the United States and Canada.[37]
The majority of bald eagles in Canada are found along the British Columbia coast while large populations are found in the forests of Alberta, Saskatchewan, Manitoba and Ontario.[38] Bald eagles also congregate in certain locations in winter. From November until February, one to two thousand birds winter in Squamish, British Columbia, about halfway between Vancouver and Whistler. In March 2024, bald eagles were found nesting in Toronto for the first time.[39] The birds primarily gather along the Squamish and Cheakamus Rivers, attracted by the salmon spawning in the area.[40] Similar congregations of wintering bald eagles at open lakes and rivers, wherein fish are readily available for hunting or scavenging, are observed in the northern United States.[41]
It has occurred as a vagrant twice in Ireland; a juvenile was shot illegally in Fermanagh on January 11, 1973 (misidentified at first as a white-tailed eagle), and an exhausted juvenile was captured near Castleisland, County Kerry on November 15, 1987.[42] There is also a record of it from Llyn Coron, Anglesey, in the United Kingdom, from October 17, 1978;[43] the provenance of this individual eagle has remained in dispute.
Habitat
In flight during a licensed performance in Ontario, CanadaDuring training at the Canadian Raptor Conservancy
The bald eagle occurs during its breeding season in virtually any kind of American wetland habitat such as seacoasts, rivers, large lakes or marshes or other large bodies of open water with an abundance of fish. Studies have shown a preference for bodies of water with a circumference greater than 11km (7mi), and lakes with an area greater than 10km2 (4sqmi) are optimal for breeding bald eagles.[44]
The bald eagle typically requires old-growth and mature stands of coniferous or hardwood trees for perching, roosting, and nesting. Tree species reportedly is less important to the eagle pair than the tree's height, composition and location.[45] 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 20m (66ft) tall, an open structure, and proximity to prey. If nesting trees are in standing water such as in a mangrove swamp, the nest can be located fairly low, at as low as 6m (20ft) above the ground.[46] In a more typical tree standing on dry ground, nests may be located from 16 to 38m (52 to 125ft) in height. In Chesapeake Bay, nesting trees averaged 82cm (32in) in diameter and 28m (92ft) in total height, while in Florida, the average nesting tree stands 23m (75ft) high and is 23cm (9.1in) in diameter.[47][48] Trees used for nesting in the Greater Yellowstone area average 27m (89ft) high.[49] 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.[44] Most nests have been found within 200m (660ft) of open water. The greatest distance from open water recorded for a bald eagle nest was over 3km (1.9mi), in Florida.[18]
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 nearly 10 feet wide and 20 feet deep.[50]
In Florida, nesting habitats often consist of Mangrove swamps, the shorelines of lakes and rivers, pinelands, seasonally flooded flatwoods, hardwood swamps, and open prairies and pastureland with scattered tall trees. Favored nesting trees in Florida are slash pines (Pinus elliottii), longleaf pines (P. palustris), loblolly pines (P. taeda) and cypress trees, but for the southern coastal areas where mangroves are usually used.[46] In Wyoming, groves of mature cottonwoods 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.[18] In Southeast Alaska, Sitka spruce (Picea sitchensis) provided 78% of the nesting trees used by eagles, followed by hemlocks (Tsuga) at 20%.[45] Increasingly, eagles nest in human-made reservoirs stocked with fish.[46]
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 1.2km (0.75mi) from low-density human disturbance and more than 1.8km (1.1mi) from medium- to high-density human disturbance.[44] However, bald eagles will occasionally nest in large estuaries or secluded groves within major cities, such as Hardtack Island on the Willamette River in Portland, Oregon or John Heinz National Wildlife Refuge at Tinicum in Philadelphia, Pennsylvania, which are surrounded by a great quantity of human activity.[51][52] Even more contrary to the usual sensitivity to disturbance, a family of bald eagles moved to the Harlem neighborhood in New York City in 2010.[53]
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-sized mammals, such as prairies, meadows or tundra, or open forests with regular carrion access.[18][45]
Behavior
The bald eagle is a powerful flier, and soars on thermal convection currents. It reaches speeds of 56–70km/h (35–43mph) when gliding and flapping, and about 48km/h (30mph) while carrying fish.[54] Its dive speed is between 120–160km/h (75–99mph), though it seldom dives vertically.[55] Regarding their flying abilities, despite being morphologically less well adapted to faster flight than golden 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.[29] It is partially migratory, 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.[56] 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 8:00a.m. and 6:00p.m., when thermals are produced by the sun.[14]
Diet and feeding
The bald eagle is an opportunistic carnivore with the capacity to consume a great variety of prey. Fish often comprise most of the eagle's diet throughout their range.[57] 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%.[58] More than 400 species are known to be included in the bald eagle's prey spectrum, far more than its ecological equivalent in the Old World, the white-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 the red-tailed hawk, in number of prey species recorded.[29][58][59][60]
To hunt fish, the eagle swoops down over the water and snatches the fish out of the water with its talons. 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. Osprey also have this adaptation.[54] Bird prey may occasionally be attacked in flight, with prey up to the size of Canada geese attacked and killed in mid-air.[61] It has been estimated that the gripping power (pounds by square inch) of the bald eagle is ten times greater than that of a human.[62] 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 are able to swim, in some cases dragging its catch ashore with its talons, but some eagles drown or succumb to hypothermia.[63] 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.[46][64] 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.[31][29][58][59] When food is abundant, an eagle can gorge itself by storing up to 1kg (2.2lb) of food in a pouch in the throat called a crop. Gorging allows the bird to fast for several days if food becomes unavailable.[46] 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.[15][65][66] 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.[31]
They obtain much of their food as carrion or via a practice known as kleptoparasitism, 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.[18] 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.[67][68] 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 of whales, though carcasses of ungulates and large fish are seemingly preferred.[31] Congregated wintering waterfowl are frequently exploited for carcasses to scavenge by immature eagles in harsh winter weather.[69] Bald eagles also may sometimes feed on material scavenged or stolen from campsites and picnics, as well as garbage dumps (dump usage is habitual mainly in Alaska)[70] and fish-processing plants.[71]
Fish
In flight with freshly caught fishFeeding on catfish and other various fishes. Painted by John James Audubon
In Southeast 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.[73] Eagles living in the Columbia River Estuary in Oregon were found to rely on fish for 90% of their dietary intake.[74] At least 100 species of fish have been recorded in the bald eagle's diet.[59] From observation in the Columbia River, 58% of the fish were caught alive by the eagle, 24% were scavenged as carcasses and 18% were pirated away from other animals.[74]
Fish taken by bald eagles varies in size, but bald eagles take larger fish than other piscivorous birds in North America, typically range from 20 to 75cm (7.9 to 29.5in) and prefer 36cm (14in) fish.[85] When experimenters offered fish of different sizes in the breeding season around Lake Britton in California, fish measuring 34 to 38cm (13 to 15in) were taken 71.8% of the time by parent eagles while fish measuring 23 to 27.5cm (9.1 to 10.8in) were chosen only 25% of the time.[86] At nests around Lake Superior, the remains of fish (mostly suckers) were found to average 35.4cm (13.9in) in total length.[87] In the Columbia River estuary, most preyed on by eagles were estimated to measure less than 30cm (12in), but larger fish between 30 and 60cm (12 and 24in) or even exceeding 60cm (24in) in length also taken especially during the non-breeding seasons.[74] They can take fish up to at least twice their own weight, such as large mature salmons, carps, or even muskellunge (Esox masquinongy), by dragging its catch with talons and pull toward ashore.[29][58][88][89] Much larger marine fish such as Pacific halibut (Hippoglossus stenolepis) and lemon 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.[60][90]
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.[78] Bald eagles also regularly exploit water turbines which produce battered, stunned or dead fish easily consumed.[91] Predators who leave behind scraps of dead fish that they kill, such as brown bears (Ursus arctos), gray wolves (Canis lupus) and red foxes (Vulpes vulpes), may be habitually followed in order to scavenge the kills secondarily.[73] Once North Pacific salmon die off after spawning, usually local bald eagles eat salmon carcasses almost exclusively. Eagles in Washington need to consume 489g (1.078lb) of fish each day for survival, with adults generally consuming more than juveniles and thus reducing potential energy deficiency and increasing survival during winter.[92]
Behind fish, the next most significant prey base for bald eagles are other waterbirds. 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.[74][93] Overall, birds are the most diverse group in the bald eagle's prey spectrum, with 200 prey species recorded.[29][59][60]
Bird species most preferred as prey by eagles tend to be medium-sized, such as western grebes (Aechmophorus occidentalis), mallards (Anas platyrhynchos), and American coots (Fulica americana) as such prey is relatively easy for the much larger eagles to catch and fly with.[18][74] American herring gull (Larus smithsonianus) are the favored avian prey species for eagles living around Lake Superior.[87]Black ducks (Anas rubripes), common eiders (Somateria mollissima), and double-crested cormorants (Phalacrocorax auritus) are also frequently taken in coastal Maine[80] and velvet scoter (Melanitta fusca) was dominant prey in San Miguel Island.[94]
A bald eagle prepares to pick off a common murre from Colony Rock in Oregon Islands National Wildlife Refuge, Oregon, United States.
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.[95] Along some portions of the North Pacific coastline, bald eagles which had historically preyed mainly kelp-dwelling fish and supplementally sea 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.[96] Because of this more extensive predation, some biologist has expressed concern that murres are heading for a "conservation collision" due to heavy eagle predation.[95] Eagles have been confirmed to attack nocturnally active, burrow-nesting seabird species such as storm petrels and shearwaters by digging out their burrows and feeding on all animals they find inside.[97] 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 as gulls.[95]
While they usually target small to medium-sized seabirds, larger seabirds such as great black-backed gulls (Larus marinus) and northern gannets (Morus bassanus) and brown pelicans (Pelecanus occidentalis) of all ages can successfully be taken by bald eagles.[98][99][100] Similarly, large waterbirds are occasionally killed. Geese such as wintering emperor geese (Chen canagica) and snow geese (C. caerulescens), which gather in large groups, sometimes becoming regular prey.[31][64] Smaller Ross's geese (Anser rossii) are also taken, as well as large-sized Canada geese (Branta canadensis).[101][78] Predation on the largest subspecies (Branta canadensis maxima) has been reported.[102] Other large waterbird prey include common loons (Gavia immer) of all ages. [103] Large wading birds can also fall prey to bald eagles. For the great blue herons (Ardea herodias), bald eagles are their only serious enemies of all ages.[58][104] Slightly larger Sandhill cranes (Grus canadensis) can be taken as well.[105] While adult whooping cranes (Grus americana) are too large and formidable, their chicks can fall prey to bald eagles.[106][107][108] They even occasionally prey on adult tundra swans (Cygnus columbianus).[109] Young trumpeter swans (Cygnus buccinator) are also taken, and an unsuccessful attack on an adult swan has been photographed.[110][111]
Bald eagles have been occasionally recorded as killing other raptors. In some cases, these may be attacks of competition or kleptoparasitism on rival species but end with the consumption of the dead victims. Nine species of other accipitrids and owls are known to have been preyed upon by bald eagles. Owl prey species have ranged in size from western screech-owls (Megascops kennicotti) to snowy owls (Bubo scandiacus).[29][59][60][112] Larger diurnal raptors known to have fallen victim to bald eagles have included red-tailed hawks (Buteo jamaicensis),[113]peregrine falcons (Falco peregrinus),[114]northern goshawks (Accipiter gentilis),[115]ospreys (Pandion haliaetus)[116] and black (Coragyps atratus) and turkey vultures (Cathartes aura).[117]
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 as prairie dogs (Cynomys sp.) and jackrabbits (Lepus sp.).[18][118] Bald eagles in Seedskadee National Wildlife Refuge often hunt in pair to catch cottontails, jackrabbits and prairie dogs.[119] They can attack and prey on rabbits and hares of nearly any size, from marsh rabbits (Sylvilagus palustris) to black and white-tailed jackrabbits (Lepus californicus & L. townsendii), and Arctic hares (Lepus arcticus).[120][121][84] In San Luis Valley, white-tailed jackrabbits can be important prey.[109] Additionally, rodents such as montane voles (Microtus montanus), brown rats (Rattus norvegicus), and various squirrels are taken as supplementary prey.[121][14][80] Larger rodents such as muskrats (Ondatra zibethicus), young or small adult nutrias (Myocastor coypus) and groundhogs (Marmota monax) are also preyed upon.[122][123] Even American porcupines (Erethizon dorsatum) are reportedly attacked and killed.[124]
Other wild mammalian prey include fawns of deer such as white-tailed deer (Odocoileus virginianus) and Sitka deer (Odocoileus hemionus sitkensis), which weigh around 3kg (6.6lb) can be taken alive by bald eagles.[139][140] In one instance, a bald eagle was observed carrying 6.8kg (15lb)mule deer (Odocoileus hemionus) fawn.[141] Additionally, Virginia opossums (Didelphis virginiana) can be preyed upon. Still, predation events are rare due to their nocturnal habits.[120][142][132]
Together with the golden eagle, bald eagles are occasionally accused of preying on livestock, especially sheep (Ovis aries). There are a handful of proven cases of lamb predation, some specimens weighing up to 11kg (24lb), 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.[143] 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 3 other eagles), which, weighing on average over 60kg (130lb), is much larger than any other known prey taken by this species.[144]
Reptiles and other prey
Supplemental prey is readily taken given the opportunity. In some areas, reptiles may become regular prey, especially in warm areas such as Florida where reptile diversity is high. Turtles are perhaps the most regularly hunted type of reptile.[18] In coastal New Jersey, 14 of 20 studied eagle nests included remains of turtles. The main species found were common musk turtles (Sternotherus odoratus), diamondback terrapin (Malaclemys terrapin) and juvenile common snapping turtles (Chelydra serpentina). In these New Jersey nests, mainly subadult and small adults were taken, ranging in carapace length from 9.2 to 17.1cm (3.6 to 6.7in).[145] Similarly, many turtles were recorded in the diet in the Chesapeake Bay.[146] In Texas, softshell turtles are the most frequently taken prey,[147] and a large number of Barbour's map turtles are taken in Torreya State Park.[148] Other reptilian and amphibian prey includes southern alligator lizards (Elgaria multicarinata),[94] snakes such as garter snakes and rattlesnakes,[46][149][150][84] and Greater siren (Siren lacertina).[120]
When competing for food, eagles will usually dominate other fish-eaters and scavengers, aggressively displacing mammals such as coyotes (Canis latrans) and foxes, and birds such as corvids, gulls, vultures and other raptors.[70] 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.[152] 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).[94][19] 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.[31] Wintering bald and golden eagles in Utah both sometimes won conflicts, though in one recorded instance a single bald eagle successfully displaced two consecutive golden eagles from a kill.[153]
Though bald eagles face few natural threats, an unusual attacker comes in the form of the common 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 fatal puncture wound inflicted by one or both loon parents.[154]
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 golden eagles there are estimated to live in North America.[19][37] Due to this, bald eagles often outnumber golden eagles at attractive food sources.[19] Despite the potential for contention between these animals, in New Jersey during winter, a golden eagle and numerous bald eagles were observed to hunt snow 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 eastern Appalachian Mountains without apparent conflict.[19] Bald eagles are frequently mobbed by smaller raptors, due to their infrequent but unpredictable tendency to hunt other birds of prey.[153] 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 even otters.[31][155] They have also been recorded opportunistically pirating birds from peregrine falcons (Falco peregrinus), prairie dogs from ferruginous hawks (Buteo regalis) and even jackrabbits from golden eagles.[156][157] 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.[46] Healthy adult bald eagles are not preyed upon in the wild and are thus considered apex predators.[158]
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 generally mate 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.[159] Bald eagle courtship involves elaborate, spectacular calls and flight displays by the males. The flight includes swoops, chases, and cartwheels, in which they fly high, lock talons, and free-fall, separating just before hitting the ground.[58][160][161] Usually, a territory defended by a mature pair will be 1 to 2km (0.62 to 1.24mi) of waterside habitat.[18]
Mating
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.[18] The nest is the largest of any bird in North America; it is used repeatedly over many years and with new material added each year may eventually be as large as 4m (13ft) deep, 2.5m (8.2ft) across and weigh 1 metric ton (1.1 short tons).[10] One nest in Florida was found to be 6.1m (20ft) deep, 2.9 meters (9.5ft) across, and to weigh 3 short tons (2.7 metric tons).[162] This nest is on record as the largest tree nest ever recorded for any animal.[163] 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 the Midwest was occupied continuously for at least 34 years.[46] The nest is built of branches, 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 as Amchitka Island in Alaska.[70]
In Sonora, Mexico, eagles have been observed nesting on top of hecho catcuses (Pachycereus pectin-aboriginum).[164] Nests located on cliffs and rock pinnacles have been reported historically in California, Kansas, Nevada, New Mexico and Utah, but currently are only verified to occur only in Alaska and Arizona.[18] The eggs average about 73mm (2.9in) long, ranging from 58 to 85mm (2.3 to 3.3in), and have a breadth of 54mm (2.1in), ranging from 47 to 63mm (1.9 to 2.5in).[54][58] Eggs in Alaska averaged 130g (4.6oz) in mass, while in Saskatchewan they averaged 114.4g (4.04oz).[165][166] As with their ultimate body size, egg size tends to increase with distance from the equator.[58] 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 of polygyny.[133] Eagles in captivity have been capable of producing up to seven eggs.[167] 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.[18] 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.[18] 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 genus Aquila, in which a second fledgling is typically observed in less than 20% of nests, despite two eggs typically being laid.[28] 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).[18]
A young eaglet can gain up to 170g (6.0oz) a day, the fastest growth rate of any North American bird.[46] 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.[46] 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 6 weeks. Juvenile eagles first start dispersing away from their parents about 8 weeks after they fledge. Variability in departure date related to effects of sex and hatching order on growth and development.[166] For the next four years, immature eagles wander widely in search of food until they attain adult plumage and are eligible to reproduce.[168]
Male eagles have been observed killing and cannibalizing their chicks.[169] In 2024 at the National Conservation Training Center in West 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."[170]
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 near Sidney, British Columbia. The pair of eagles in question are believed to have carried a juvenile red-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.[171] The hawk, nicknamed "Spunky" by biologists monitoring the nest, fledged successfully.[172]
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.[173] In captivity, they often live somewhat longer. In one instance, a captive individual in New York lived for nearly 50 years.[174] As with size, the average lifespan of an eagle population appears to be influenced by its location and access to prey.[175] As they are no longer heavily persecuted, adult mortality is quite low. In one study of Florida eagles, adult bald eagles reportedly had 100% annual survival rate.[19] In Prince William Sound in Alaska, adults had an annual survival rate of 88% even after the Exxon Valdez oil spill adversely affected eagles in the area.[176] Of 1,428 individuals from across the range necropsied by National 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.[177] In this study, 68% of mortality was human-caused.[177] Today, eagle-shooting is believed to be considerably reduced due to the species' protected status.[178] A U.S. Fish and Wildlife Service study of 1,490 bald eagle deaths from 1986 through 2017 in Michigan found that 532 (36%) died due to being struck by cars while scavenging roadkill and 176 (12%) died due to lead poisoning from ingesting fragments of lead ammo and fishing gear present in carrion, with the proportion of both causes of death increasing significantly towards the end of the study period.[179][180]
Most non-human-related mortality involves nestlings or eggs. Around 50% of eagles survive their first year.[168] However, in the Chesapeake Bay area, 100% of 39 radio-tagged nestlings survived to their first year.[181] 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 large gulls, corvids (including ravens, crows and magpies), wolverines (Gulo gulo), fishers (Pekania pennanti), red-tailed hawks, owls, other eagles, bobcats, American black bears (Ursus americanus) and raccoons.[165][182][183][184][109][185][186][187] 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.[28] Nestlings are usually exempt from predation by terrestrial carnivores that are poor tree-climbers, but Arctic foxes (Vulpes lagopus) occasionally snatched nestlings from ground nests on Amchitka Island in Alaska before they were extirpated from the island.[70] The bald eagle will defend its nest fiercely from all comers and has even repelled attacks from bears, having been recorded knocking a black bear out of a tree when the latter tried to climb a tree holding nestlings.[188]
Relationship with humans
Population decline and recovery
Inside a waste collection and transfer facility, in Homer, 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 pesticide DDT.[189] Bald eagles, like many birds of prey, were especially affected by DDT due to biomagnification. DDT itself was not lethal to the adult bird, but it interfered with their calcium metabolism, making them either sterile or unable to lay healthy eggs; many of their eggs were too brittle to withstand the weight of a brooding adult, making it nearly impossible for them to hatch.[35] It is estimated that in the early 18th century the bald eagle population was 300,000–500,000,[190] but by the 1950s there were only 412 nesting pairs in the 48 contiguous states of the US.[191][192] Other factors in bald eagle population reductions were a widespread loss of suitable habitat, as well as both legal and illegal shooting. In 1930 a New York City ornithologist wrote that in the territory of Alaska 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 young lambs 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).[193] Illegal shooting was described as "the leading cause of direct mortality in both adult and immature bald eagles" by the U.S. Fish and Wildlife Service in 1978.[194] Leading causes of death in bald eagles include lead pollution, poisoning, collision with motor vehicles, and power-line electrocution.[195] A study published in 2022 in the journal Science found that more than half of adult eagles across 38 US states suffered from lead poisoning.[196] The primary cause is when eagles scavenge carcasses of animals shot by hunters.[196] These are often tainted with lead shotgun pellets, rifle rounds, or fishing tackle.[196][180]
The species was first protected in the U.S. and Canada by the 1918 Migratory Bird Treaty, later extended to all of North America. The Bald and Golden Eagle Protection Act, approved by the U.S. Congress in 1940, protected the bald eagle and the golden eagle, prohibiting commercial trapping and killing of the birds. 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.[197][198] 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.[199] DDT was completely banned in Canada in 1989, though its use had been highly restricted since the late 1970s.[200]
First-year juvenile bald eagle at Anacortes, 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;[10] the U.S. state with the largest resident population is Alaska, with about 40,000–50,000, with the next highest population the Canadian province of British Columbia with 20,000–30,000 in 1992.[10] 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.[201] For some time, the stronghold breeding population of bald eagles in the lower 48 states was in Florida, 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 is Minnesota 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.[37] In Washington 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 the Washington Department of Fish and Wildlife counted occupied nests. Further population increases in Washington may be limited by the availability of late winter food, particularly salmon.[202]
The bald eagle was officially removed from the U.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.[203] It has also been assigned a risk level of least concern category on the IUCN Red List.[2] In the Exxon Valdez oil spill of 1989 an estimated 247 were killed in Prince William Sound, though the local population returned to its pre-spill level by 1995.[15] In some areas, the increase in eagles has led to decreases in other bird populations[204] and the eagles may be considered a pest.[205]
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 5-year term.[206][207]
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.[208] The bald eagle can be long-lived in captivity if well cared for, but does not breed well even under the best conditions.[209]
In Canada[210] and in England[211] a license is required to keep bald eagles for falconry.[212] 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.[213][214]
Cultural significance
The bald eagle is important in various Native American cultures and, as the national symbol of the United States, is prominent in seals and logos, coinage, postage stamps, and other items relating to the U.S. federal government.
Role in Native American culture
The bald eagle is a sacred bird in some North American cultures, and its feathers, like those of the golden eagle, are central to many religious and spiritual customs among Native Americans. Eagles are considered spiritual messengers between gods and humans by some cultures.[215] Many pow wow dancers use the eagle claw 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 the Navajo 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.[216] The Lakota, 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.[217] The Pawnee consider eagles as symbols of fertility because their nests are built high off the ground and because they fiercely protect their young.[218] The Choctaw consider the bald eagle, who has direct contact with the upper world of the sun, as a symbol of peace.[219]
During the Sun Dance, which is practiced by many Plains 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, a medicine 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.[220]
Current 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 the First Amendment by affecting ability to practice their religion freely.[221][222]
The National Eagle Repository, a division of the FWS, 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 to federally recognized Native American tribes for use in religious ceremonies.[223]
The bald eagle appears on most official seals of the U.S. government, including the presidential seal, the presidential 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 the urban legend that the flag is changed to have the eagle face towards the olive branch in peace, and towards the arrows in wartime.[228]
Contrary to popular legend, there is no evidence that Benjamin Franklin ever publicly supported the wild 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 the Society of the Cincinnati, he stated his personal distaste for the bald eagle's behavior. In the letter Franklin states:[229]
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 little king 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 a noble order unwelcome in the newly independent Republic, contrary to the ideals of Lucius 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.[230]
Popular culture
Largely because of its role as a symbol of the United States, but also because of its being a large predator, the bald eagle has many representations in popular culture. In film and television depictions the call of the red-tailed hawk, which is much louder and more powerful, is often substituted for bald eagles.[231]
The golden eagle is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known birds of prey in the Northern Hemisphere. These birds are dark brown, with lighter golden-brown plumage on their napes. Immature eagles of this species typically have white on the tail and often have white markings on the wings. Golden eagles use their agility and speed combined with powerful feet and large, sharp talons to hunt a variety of prey, mainly hares, rabbits, and marmots and other ground squirrels. Golden eagles maintain home ranges or territories that may be as large as 200 km2 (77 sq mi). They build large nests in cliffs and other high places to which they may return for several breeding years. Most breeding activities take place in the spring; they are monogamous and may remain together for several years or possibly for life. Females lay up to four eggs, and then incubate them for six weeks. Typically, one or two young survive to fledge in about three months. These juvenile golden eagles usually attain full independence in the fall, after which they wander widely until establishing a territory for themselves in four to five years.
The eastern imperial eagle is a large bird of prey that breeds in southeastern Europe and extensively through West and Central Asia. Most populations are migratory and winter in northeastern Africa, the Middle East and South and East Asia. Like all eagles, the eastern imperial eagle is a member of the family Accipitridae. Furthermore, its feathered legs mark it as a member of the subfamily Aquilinae. It is a large, dark-colored eagle, with a resemblance to other members of the genus Aquila but it is usually the darkest species in its range. This is an opportunistic predator that mostly selects smallish mammals as prey but also a fairly large proportion of birds, reptile and other prey types, including carrion. Compared to other Aquila eagles, it has a strong preference for the interface of tall woods with plains and other open, relatively flat habitats, including the wooded mosaics of the steppe. Normally, nests are located in large, mature trees and the parents raise around one or two fledglings. The global population is small and declining due to persecution, loss of habitat and prey. It has therefore been IUCN Red Listed as Vulnerable since 1994.
The great blue heron is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America, as well as far northwestern South America, the Caribbean and the Galápagos Islands. It is occasionally found in the Azores and is a rare vagrant to Europe. An all-white population found in south Florida and the Florida Keys is known as the great white heron. Debate exists about whether these white birds are a color morph of the great blue heron, a subspecies of it, or an entirely separate species.
The wedge-tailed eagle also known as the eaglehawk, is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. Adults of the species have long, broad wings, fully feathered legs, an unmistakable wedge-shaped tail, an elongated upper mandible, a strong beak and powerful feet. The wedge-tailed eagle is one of 12 species of large, predominantly dark-coloured booted eagles in the genus Aquila found worldwide. Genetic research has clearly indicated that the wedge-tailed eagle is fairly closely related to other, generally large members of the Aquila genus. A large brown-to-black bird of prey, it has a maximum reported wingspan of 2.84 m and a length of up to 1.06 m.
The white-tailed eagle, sometimes known as the 'sea eagle', is a large bird of prey, widely distributed across temperate Eurasia. Like all eagles, it is a member of the family Accipitridae which also includes other diurnal raptors such as hawks, kites, and harriers. One of up to eleven members in the genus Haliaeetus, which are commonly called sea eagles, it is also referred to as the white-tailed sea-eagle. Sometimes, it is known as the ern or erne, gray sea eagle and Eurasian sea eagle.
The white-bellied sea eagle, also known as the white-breasted sea eagle, is a large diurnal bird of prey in the family Accipitridae. Originally described by Johann Friedrich Gmelin in 1788, it is closely related to Sanford's sea eagle of the Solomon Islands, and the two are considered a superspecies. A distinctive bird, the adult white-bellied sea eagle has a white head, breast, under-wing coverts and tail. The upper parts are grey and the black under-wing flight feathers contrast with the white coverts. The tail is short and wedge-shaped as in all Haliaeetinae species. Like many raptors, the female is larger than the male, and can measure up to 90 cm (35 in) long with a wingspan of up to 2.2 m (7.2 ft), and weigh 4.5 kg (9.9 lb). Immature birds have brown plumage, which is gradually replaced by white until the age of five or six years. The call is a loud goose-like honking.
The great black-backed gull is the largest member of the gull family. Described by the Cornell Lab of Ornithology as "the king of the Atlantic waterfront", it is a very aggressive hunter, pirate, and scavenger. It breeds on the European and North American coasts and islands of the North Atlantic and is fairly sedentary, though some move farther south or inland to large lakes and reservoirs. The adult great black-backed gull has a white head, neck and underparts, dark grey wings and back, pink legs and yellow bill.
The rough-legged buzzard (Europe) or rough-legged hawk is a medium-large bird of prey. It is found in arctic and subarctic regions of North America, Europe, and Asia during the breeding season, and migrates south for the winter. Historically, it was also known as "rough-legged falcon" in such works as John James Audubon's The Birds of America.
The red-tailed hawk is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members within the genus of Buteo in North America or worldwide. The red-tailed hawk is one of three species colloquially known in the United States as the "chickenhawk", though it rarely preys on standard-sized chickens. The bird is sometimes also referred to as the red-tail for short, when the meaning is clear in context.
The ferruginous hawk is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk.
The African fish eagle or the African sea eagle is a large species of eagle found throughout sub-Saharan Africa wherever large bodies of open water with an abundant food supply occur. It is the national bird of Malawi, Namibia, Zambia, and Zimbabwe. As a result of its large range, it is known in many languages. Examples of names include: Vis Arend in Afrikaans, nkwazi in Chewa, aigle pêcheur in French, hungwe in Shona, inkwazi in isiZulu, and ntšhu in Northern Sotho. This species may resemble the bald eagle in appearance; though related, the two species occur on different continents, with the bald eagle being resident in North America.
Steller's sea eagle, also known as the Pacific sea eagle or white-shouldered eagle, is a very large diurnal bird of prey in the family Accipitridae. It was described first by Peter Simon Pallas in 1811. No subspecies are recognised. A sturdy eagle, it has dark brown plumage with white wings and tail, a yellow beak, and yellow talons. Typically, it is the heaviest eagle in the world, at about 5 to 10 kg, but in some standard measurements, may be ranked below the harpy eagle and the Philippine eagle. Steller's sea eagle females are bigger than males.
Pallas's fish eagle, also known as Pallas's sea eagle or band-tailed fish eagle, is a large, brownish sea eagle. It breeds in the east Palearctic in Kazakhstan, Russia, Tajikistan, Turkmenistan, Uzbekistan, Mongolia, China, India, Nepal, Bangladesh, Myanmar and Bhutan. It is listed as Endangered on the IUCN Red List. It is partially migratory, with Central Asian birds wintering among the southern Asian birds in northern India, and also further west to the Persian Gulf.
The martial eagle is a large eagle native to sub-Saharan Africa. It is the only member of the genus Polemaetus. A species of the booted eagle subfamily (Aquilinae), it has feathers over its tarsus. One of the largest and most powerful species of booted eagle, it is a fairly opportunistic predator that varies its prey selection between mammals, birds and reptiles. It is one of few eagle species known to hunt primarily from a high soar, by stooping on its quarry. This species, an inhabitant of wooded belts of otherwise open savanna, has shown a precipitous decline in the last few centuries due to a variety of factors. The martial eagle is one of the most persecuted bird species in the world. Due to its habit of taking livestock and regionally valuable game, local farmers and game wardens frequently seek to eliminate martial eagles, although the effect of eagles on this prey is almost certainly considerably exaggerated. Currently, the martial eagle is classified with the status of Endangered by the IUCN.
The golden eagle is one of the most powerful predators in the avian world. One author described it as "the pre-eminent diurnal predator of medium-sized birds and mammals in open country throughout the Northern Hemisphere". Golden eagles usually hunt during daylight hours, but were recorded hunting from one hour before sunrise to one hour after sunset during the breeding season in southwestern Idaho. The hunting success rate of golden eagles was calculated in Idaho, showing that, out of 115 hunting attempts, 20% were successful in procuring prey. A fully-grown golden eagle requires about 230 to 250 g of food per day. In the life of most eagles, there are cycles of feast and famine, and eagles have been known to go without food for up to a week. Following these periods without food, they will then gorge on up to 900 g (2.0 lb) at one sitting. The powerful talons of the golden eagle ensure that few preys can escape them once contact is made. The talons of this species exert approximately 440 pounds per square inch (3 MPa) of pressure, around 15 times more pressure than is exerted by the human hand, although some claim that the largest individual females may reach a pressure of 750 psi (5.2 MPa). It has been claimed that the golden eagle can lift more than its own body weight in flight. However, other sources claim that a hare, marmot or deer calf weighing 4 kg (8.8 lb) is a struggle for even a large female to carry and that prey much over 2 kg (4.4 lb) would require favorably high wind conditions.
The Eurasian goshawk is a species of medium-large bird of prey in the family Accipitridae, a family which also includes other extant diurnal raptors, such as eagles, buzzards and harriers. It was formerly placed in the genus Accipiter. It is a widespread species that inhabits many of the temperate parts of the Eurasia. Except in a small portion of southern Asia, it is the only species of "goshawk" in its range and it is thus often referred to, both officially and unofficially, as simply goshawk. It is mainly resident, but birds from colder regions migrate south for the winter. As of 2023, goshawks found in North America are no longer considered be conspecific, but are now designated as the American goshawk.
The crowned eagle, also known as the African crowned eagle or the crowned hawk-eagle, is a large bird of prey found in sub-Saharan Africa; in Southern Africa, it is restricted to more easterly areas. Its preferred habitats are principally riparian woodlands and various forests. The crowned eagle is the only extant member of the genus Stephanoaetus. A second species, the Malagasy crowned eagle, went extinct after early humans settled on Madagascar.
Golden eagles usually mate for life. A breeding pair is formed in a courtship display. This courtship includes undulating displays by both in the pair, with the male bird picking up a piece of rock and dropping it only to enter into a steep dive and catch it in mid-air, repeating the maneuver 3 or more times. The female takes a clump of earth and drops and catches it in the same fashion. Small sticks may also be used in this display. Compared to the bald eagle, golden eagles do not repeat courtship displays annually and rarely engage in talon-locking downward spirals.
At one time, the golden eagle lived in a great majority of temperate Europe, North Asia, North America, North Africa, and Japan. Although widespread and quite secure in some areas, in many parts of the range golden eagles have experienced sharp population declines and have even been extirpated from some areas. The total number of individual golden eagles from around the range is estimated to range somewhere between 170,000 and 250,000 while the estimated total number of breeding pairs ranges from 60,000 to 100,000. Few other eagle species are as numerous, though some species like tawny eagle, wedge-tailed eagle and bald eagle have total estimated populations of a similar size to the golden eagle's despite having distributions which are more restricted. The world's most populous eagle may be the African fish eagle, which has a stable total population estimated at 300,000 individuals and is found solely in Africa. On a global scale, the golden eagle is not considered threatened by the IUCN.
The dusky Canada goose is a subspecies of the Canada goose. They are the darkest variant, similar to the Pacific cackling goose. Tagged dusky geese have red bands with white letters on them attached to their neck. They represent one of the smallest populations of Canada goose in the Pacific Northwest. Due to the species' minimal population and exclusive breeding grounds, the dusky Canada goose is a species of interest to the Pacific Flyway Council and the U.S. Forest Service. The Cordova Ranger District, on the Chugach National Forest, has been working since 1984 to implement a monitoring and restoration program for the geese.
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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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