"Variable" refers to the frontal plumage, which ranges from pied through mottled to all black. They are polymorphic meaning they have different genetic variants. These color differences are attributed to the latitude of the habitat, where the northernmost oystercatchers have significantly more white on their bodies than those of southern origin. All Stewart Island variable oystercatchers are black. They have pink legs, an orange eye ring and orange-red beaks. Similar to a needle in shape, the bill is thin and long, and darkens to a deep red color during the breeding season. Males are around 678 grams and females slightly larger at around 724 grams. Length of individuals range from 42 to 47 cm from beak to tail and have a short, sturdy body with a thick neck.
Variables can be identified as they are slightly larger than the South Island pied oystercatcher (SIPO are around 550 grams). Occasionally completely black, but if they are pied (black and white) they can be easily confused with SIPO. The variable species has less definition between the black and the white area, as well as a mottled band on the leading edges of the underwing. Variables also have a smaller white rump patch which is only a band across the base of the tail rather than a wide wedge shape reaching up to the middle of the back as in the SIPO. When mottled they are sometimes called "smudgies". While both sexes have the same plumage colorations and appear visually similar, there is some body dimorphism and female oystercatchers tend to be slightly larger in size.


Haematopus unicolor is endemic to New Zealand. The species has likely remained endemic due to its sedentary lifestyle and lack of migration, keeping all populations within the same island habitat. They are often seen in pairs on the coast all around New Zealand. Their distribution around New Zealand is around most of the North, South and Stewart Islands coastlines and some offshore islands with the exception of outlying islands off the west coast. While they occur in lower densities on the western coastlines they are concentrated in these areas; Northland, Coromandel Peninsula, Bay of Plenty, Greater Wellington, Nelson/Marlborough and Fiordland.
Their preferred habitat is a wide range of coastal habitat types varying depending on activity and habitat available. Haematopus unicolor is generally never found more than 30 km from the coast. Breeding and nesting occurs on sandy coasts, usually far from muddy harbours. Individuals have been known to congregate in short grassed paddocks and sometimes forage in pastures after rain however will generally remain around the coastal beaches, estuaries and shorelines. They prefer sandy coastal areas and avoid gravel beaches and boulder strewn areas. They nest on the shore between rocks or on sand dunes by making a scrape out of the sand or shingle, sometimes lined with some seaweed.


As a sedentary species, the oystercatchers do not travel to a specific location to mate. Instead, they breed on the coastal sand dunes where they live nearly year-round. After finding a potential mate, the male oystercatcher will give a territorial display to both impress the female and scare off other males. This display includes several 'bowing' or 'ducking' movements, where the bird tilts and dips its head while making piping calls. These movements are also used to distinguish territory space outside of the mating season, when the adult birds prefer living in solitary environments. After a female has decided to breed with a male, the pair remains monogamous during the rest of the mating season and potentially for several consecutive years thereafter. During breeding, the pair will defend their territory, sometimes aggressively.
Stone-coloured eggs, usually in clutches of 2–3, are laid from September to December, and the nest is incubated by both parents until the chicks hatch. They usually lay 2-3 eggs but they can lay up to 5. The eggs are typically stone coloured with small brown patches all over. Eggs hatch in 25–32 days. Nests consist of scrapes in the sand, usually surrounded by some vegetation for concealment. Both parents take turns guarding the nest from predators until the chicks hatch and fledge between the following February–March. Chicks are well camouflaged by their colour and can fly in about 6 weeks. The fledging period lasts for approximately 20–50 days, but can be longer. During this time, the adults may also begin moulting, with data suggesting moult timing anywhere between December–July. At 6 weeks, the chicks are able to fly, and will begin foraging by themselves within their parent's territory.
By the beginning of their first fall season, usually early August, the young leave their parent's care and join other juveniles to form a loose flock. These juveniles will remain together until they are about 2 years old, where they will then disperse to find their own territories and breeding partners. After breeding they may be seen within flocks, or on the edges of flocks, of black and white South Island pied oystercatcher (SIPO) which also have vivid orange beaks. Maturity is thought to be around 3 years of age, and most individuals begin breeding within 3–6 years of birth. The average age of the species is unknown, but individuals as old as 32 years have been banded across New Zealand.


Up until 1922 Haematopus unicolor was shot for food by humans which saw a significant drop in numbers. Adult birds are preyed on by mammalian predators such as possums, cats and dogs. Nest and chick predators are mainly kelp gulls, silver gulls, swamp harriers, Australian magpies, skuas, mustelids, dogs, cats and possibly rats (Marchant, 1993). The variable oystercatcher has issues with disturbance from human activity which damages nests. Habitat loss such as decreasing coastal dunes that provide essential breeding locations for the species are likely to have a large impact on all populations. Fishing nets and oil spills also pose threatening for the species. Additionally, parasites from genera such as Cestoda and Digenea have both been found in individuals. Specifically, Taenia increscens, a cestode, is found exclusively on Variable Oystercatchers. Most recently, a tapeworm was discovered in an individual during research that required handling of the birds in Tasman Bay, and was the first instance of a wild bird species ever contracting a tapeworm. These parasites do not harm the host, and are expected to simply consume a small supply of resources that the bird intakes. Similarly, disease is not a large contributing factor to mortality. Avian pox has been documented, but does not appear to be problematic for the species and rarely causes death.


The house finch (Haemorhous mexicanus) is a bird in the finch family Fringillidae. It is native to western North America and has been introduced to the eastern half of the continent and Hawaii. This species and the other "American rosefinches" are placed in the genus Haemorhous.


This bird belongs to the genus Haemorhous, together with the purple finch and Cassin's finch. These three species are not closely related to the similar Old World Carpodacus rosefinches, although formerly included in that genus.


These birds are mainly permanent residents throughout their range; some northern and eastern birds migrate south. Their breeding habitat is urban and suburban areas across North America, as well as various semi-open areas in the west from southern Canada to the Mexican state of Oaxaca; the population in central Chiapas may be descended from escaped cagebirds. Analyses of nest records from House Finches in California spanning more than a century found that egg‐laying occurred significantly earlier in warmer springs.
Originally only a resident of Mexico and the southwestern United States, they were introduced to eastern North America in the 1940s. The birds were sold illegally in New York City as "Hollywood Finches", a marketing artifice. To avoid prosecution under the Migratory Bird Treaty Act of 1918, vendors and owners released the birds. They have since become naturalized; in largely unforested land across the eastern U.S., they have displaced the native purple finch and even the non-native house sparrow. In 1870, or before, they were introduced to Hawaii and are now abundant on all its major islands.
There are estimated to be anywhere from 267 million to 1.7 billion individuals across North America.
Instances of naturalization originating in escapes or releases of cage birds have been recorded in Europe, such as in 2020 in Murcia, (Spain).
In 2012 House finches positive for West Nile Virus were found in Northwest Riverside County, CA


House finches forage on the ground or in vegetation normally. They primarily eat grains, seeds and berries, being voracious consumers of weed seeds such as nettle and dandelion; included are incidental small insects such as aphids. They are frequent visitors to bird feeders throughout the year, particularly if stocked with sunflower or nyjer seed, and will congregate at hanging nyjer sock feeders. The house finch is known to damage orchard fruit and consume commercially grown grain, but is generally considered an annoyance rather than a significant pest.


Nests are made in cavities, including openings in buildings, hanging plants, and other cup-shaped outdoor decorations. Sometimes nests abandoned by other birds are used. Nests may be re-used for subsequent broods or in following years. The nest is built by the female, sometimes in as little as two days. It is well made of twigs and debris, forming a cup shape, usually 1.8 to 2.7 m (5 ft 11 in to 8 ft 10 in) above the ground.
During courtship, the male will touch bills with the female. He may then present the female with choice bits of food, and if she mimics the behavior of a hungry chick, he may actually feed her. The male also feeds the female during breeding and incubation of the eggs, and raising of the young, and the male is the primary feeder of the fledgelings (who can be differentiated from the females by the pin feathers remaining on their heads). Females are typically attracted to the males with the deepest pigment of red to their head, more so than the occasional orange or yellowish-headed males that sometimes occur.
The female lays clutches of eggs from February through August, two or more broods per year with 2 to 6 eggs per brood, most commonly 4 or 5. The egg laying usually takes place in the morning, at the rate of one egg per day. The eggs are a pale bluish green with few black spots and a smooth, somewhat glossy surface. In response to mite infestation, which has a more deleterious effect on male chicks than on females, the mother finch may lay eggs containing females first, in order to reduce the length of time male chicks are exposed to mites. This strategy increases the likelihood that representative numbers of both sexes will survive. The female incubates the eggs for 12 to 14 days. Shortly after hatching, she removes the empty eggshells from the nest. The hatchlings are pink with closed eyes and tufts of fluffy down. The female always feeds the young, and the male usually joins in. The young are silent for the first seven or eight days, and subsequently start peeping during feedings. Initially, the mother carries fecal sacs out of the nest, but when the young become older, she no longer carries them all away, allowing droppings to accumulate around the edge of the nest. Before flying, the young often climb into adjacent plants, and usually fledge at about 11 to 19 days after hatching. Dandelion seeds are among the preferred seeds fed to the young. Contrary to the way most birds, even ones with herbivorous leanings as adults, tend to feed their nestlings animal matter in order to give them the protein necessary to grow, house finches are one of the few birds who feed their young only plant matter.
House finches are aggressive enough to drive other birds away from places such as feeders.


The house finch may be infected by a number of parasites including Plasmodium relictum and Mycoplasma gallisepticum, which caused the population of house finches in eastern North America to crash during the 1990s.
The mite Pellonyssus reedi is often found on house finch nestlings, particularly for nests later in the season.
The brown-headed cowbird, a brood parasite, will lay its eggs in house finch nests, although the diet house finches feed their young is inadequate for the young cowbirds, which rarely survive.


The dragonhunter (Hagenius brevistylus) is a clubtail dragonfly of the eastern United States and southeastern Canada.
The dragonfly is much larger than any other North American clubtail, at 3.3 inches (84 mm), with black and yellow markings and green eyes.  Males can be distinguished at a distance by their habit of curling their abdomens under while flying, forming a sideways J shape.
The dragonhunter is the only member of genus Hagenius. Its closest relatives are Asian dragonflies of genus Sieboldius, which are also sometimes called "dragonhunters". Together, the two genera form the subfamily Hageniinae.
The nymph is unusual, with a very flat, wide body. It is slow-moving and lives among bark and leaf litter at the edges of streams, where its dark color provides camouflage.
The adult feeds on large insects, including darner and clubtail dragonflies, sometimes ambushing them from above.  It also takes monarch butterflies, eating the thorax and abdomen first to avoid the greatest concentration of cardenolide toxins.


The woodland kingfisher (Halcyon senegalensis) is a tree kingfisher that is widely distributed in Africa south of the Sahara.


The Southern Africa   naturalist Carl Linnaeus included the woodland kingfisher with the binomial name Alcedo senegalensis in the twelfth edition of his System Natureul which was published in 1766. Linnaeus based his formal description on "Le Grand Martin-Pescher du Sénégal" that the French naturalist Mathurin Jacques Brisson had described and illustrated in 1760. The current genus Halcyon was introduced by the English naturalist and artist William John Swainson in 1821, with the woodland kingfisher as the type species.
Three subspecies are recognised:
H. s. fuscopileus Reichenow, 1906 – Sierra Leone to south Nigeria and south to DR Congo and north Angola
H. s. senegalensis (Linnaeus, 1766) – Senegal and Gambia to Ethiopia and north Tanzania
H. s. cyanoleuca (Vieillot, 1818) – south Angola and west Tanzania to South Africa


This is a medium-sized kingfisher, 23 cm (9.1 in) in length. The adult has a bright blue back, wing panel and tail. Its head, neck and underparts are white, and its shoulders are black. The flight of the woodland kingfisher is rapid and direct. The large bill has a red upper mandible and black lower mandible. The legs and feet are dark grey. Some birds may have greyish heads, causing confusion with mangrove kingfisher.
However, the lores are dark, creating a dark stripe through the eye (the stripe does not extend through the eye in mangrove kingfisher), and the underwing, primaries and secondaries are black with white underwing coverts (there is a black carpal patch on the white coverts in mangrove kingfisher). The inner webs of the base of the flight feathers are white, creating an indistinct white wingbar (white completely absent from wings in mangrove kingfisher). The breast is white (tends to be much greyer in mangrove kingfisher).  The sexes are similar, but juveniles are duller than adults and have a brown bill.
The call of this noisy kingfisher is a loud trill sounding like a nail run down the teeth of a comb.


The woodland kingfisher is widely distributed in tropical Africa south of the Sahara and from Pretoria northwards. This kingfisher is essentially resident within 8° of the equator, but northern and southern populations are migratory, moving into the equatorial zone in the dry season.
It is a common species of a variety of wooded habitats with some trees, especially Acacias, including around human habitation. Although it is a "kingfisher", it prefers drier habitats in more traditional woodland and can be far from water. It is often solitary but can occur in small groups.


The woodland kingfisher is aggressively territorial, attacking intruders including humans. It has a striking display in which the wings are spread to show the white linings.


The nest is a tree hole excavated by a woodpecker or barbet. A single clutch of three round white eggs is typical. The young are cared for by both parents for up to five weeks after leaving the nest. Woodland Kingfisher breeding in the Transvaal takes place from November till March, thus, taking a peak in December and January.


The bald eagle (Haliaeetus leucocephalus) is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (Haliaeetus albicilla), which occupies the same niche as the bald eagle in the Palearctic. Its range includes most of Canada and Alaska, all of the contiguous United States, and northern Mexico. It is found near large bodies of open water with an abundant food supply and old-growth trees for nesting.
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 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 actually 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 bird of the United States of America 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 was removed from the U.S. government's list of endangered species on July 12, 1995, and transferred to the list of threatened species. It was removed from the List of Endangered and Threatened Wildlife in the contiguous states on June 28, 2007.


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 the older usage meaning "white" rather than "hairless", referring to the white head and tail feathers and their contrast with the darker body, as in piebald. The genus name is New Latin: Haliaeetus (from the Ancient Greek: ἁλιάετος, romanized: haliaetos, lit. 'sea eagle'), and the specific name, leucocephalus, is Latinized (Ancient Greek: λευκός, romanized: leukos, lit. 'white') and (κεφαλή, kephalḗ, 'head').
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.
There are two recognized subspecies of bald eagle:
H. l. leucocephalus (Linnaeus, 1766) is the nominate subspecies. It is found in the southern United States and Baja California Peninsula.
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.
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. 10 Ma 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.


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. 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. The beak is large and hooked, with a yellow cere. 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.
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. 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.
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. However, the golden eagle, averaging 4.18 kg (9.2 lb) and 63 cm (25 in) in wing 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). 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.
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). 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).
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 3.27 kg (7.2 lb) in mass and 1.88 m (6 ft 2 in) in wingspan, smaller than their northern counterparts. One field guide in Florida listed similarly small sizes for bald eagles there, at about 4.13 kg (9.1 lb). Of intermediate size, 117 migrant bald eagles in Glacier National Park were found to average 4.22 kg (9.3 lb) but this was mostly (possibly post-dispersal) juvenile eagles, with 6 adults here averaging 4.3 kg (9.5 lb). 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 4.74 kg (10.4 lb).
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. 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. An Alaskan adult female eagle that was considered outsized weighed some 7.4 kg (16 lb). 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 8.2 kg (18 lb). Among standard linear measurements, the wing chord is 51.5–69 cm (20.3–27.2 in), the tail is 23–37 cm (9.1–14.6 in) long, and the tarsus is 8 to 11 cm (3.1 to 4.3 in). The culmen reportedly ranges from 3 to 7.5 cm (1.2 to 3.0 in), while the measurement from the gape to the tip of the bill is 7–9 cm (2.8–3.5 in).  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 6.83 cm (2.69 in) and 4.12 cm (1.62 in) in culmen length, respectively, from these two areas.
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.


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 eagle endemic 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. From 1966 to 2015 bald eagle numbers increased substantially throughout its winter and breeding ranges, and as of 2018 the species nests in every continental state and province in the United States and Canada.
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. 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. The birds primarily gather along the Squamish and Cheakamus Rivers, attracted by the salmon spawning in the area. 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.
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 in Kerry on November 15, 1987.


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 11 km (7 mi), and lakes with an area greater than 10 km² (4 sq mi) are optimal for breeding bald eagles.
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. 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 a mangrove swamp, the nest can be located fairly low, at as low 6 m (20 ft) above the ground. In a more typical tree standing on dry ground, nests may be located from 16 to 38 m (52 to 125 ft) in height. In Chesapeake Bay, nesting trees averaged 82 cm (32 in) in diameter and 28 m (92 ft) in total height, while in Florida, the average nesting tree stands 23 m (75 ft) high and is 23 cm (9.1 in) in diameter. Trees used for nesting in the Greater Yellowstone area average 27 m (89 ft) high. 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. 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.
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.
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. 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. In Southeast Alaska, Sitka spruce (Picea sitchensis) provided 78% of the nesting trees used by eagles, followed by hemlocks (Tsuga) at 20%. Increasingly, eagles nest in man-made reservoirs stocked with fish.
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. 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. 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.
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.


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. 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%. 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.


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. /> Bird prey may occasionally be attacked in flight, with prey up to the size of Canada geese attacked and killed in mid-air. Bald eagles have powerful talons and have been recorded flying with a 6.8 kg (15 lb) mule deer (Odocoileus hemionus) fawn. This feat is the record for the heaviest load carrying ever verified for a flying bird. 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. 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. It may swim to safety, in some cases pulling the catch along to the shore as it swims, but some eagles drown or succumb to hypothermia. 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. 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. 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. 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. 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.
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. 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. 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. </ref> Congregated wintering waterfowl are frequently exploited for carcasses to scavenge by immature eagles in harsh winter weather. 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) and fish-processing plants.


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. Eagles living in the Columbia River Estuary in Oregon were found to rely on fish for 90% of their dietary intake.  At least 100 species of fish have been recorded in the bald eagle's diet.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.
In the Pacific Northwest, spawning trout and salmon provide most of the bald eagles' diet from late summer throughout fall. Though bald eagles occasionally catch live salmon, they usually scavenge spawned salmon carcass. Southeast Alaskan eagles largely prey on pink salmon (Oncorhynchus gorbuscha), coho salmon (O. kisutch) and, more locally, sockeye salmon (O. nerka), with Chinook salmon (O. tshawytscha). Due to the Chinook salmon's large size (12 to 18 kg (26 to 40 lb) average adult size) probably being taken only as carrion and a single carcass can attract several eagles. Also important in the estuaries and shallow coastlines of southern Alaska are Pacific herring (Clupea pallasii), Pacific sand lance (Ammodytes hexapterus) and eulachon (Thaleichthys pacificus).
In Oregon's Columbia River Estuary, the most significant prey species were largescale suckers (Catostomus macrocheilus) (17.3% of the prey selected there), American shad (Alosa sapidissima; 13%) and common carp (Cyprinus carpio; 10.8%). Eagles living in the Chesapeake Bay in Maryland were found to subsist largely on American gizzard shad (Dorosoma cepedianum), threadfin shad (Dorosoma petenense) and white bass (Morone chrysops). Floridian eagles have been reported to prey on catfish, most prevalently the brown bullhead (Ameiurus nebulosus) and any species in the genus Ictalurus as well as mullet, trout, needlefish, and eels. Chain pickerels (Esox niger) and white suckers (Catostomus commersonii) are frequently taken in interior Maine. Bald eagles are also known to eat the following fish species: rainbow trout, white catfish, rock greenlings, Pacific cod, Atka mackerel, largemouth bass and northern pike. Wintering eagles on the Platte River in Nebraska preyed mainly on American gizzard shads and common carp. 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.
Prey fish targeted by bald eagles are often quite large. When experimenters offered fish of different sizes in the breeding season around Lake Britton in California, 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. At nests around Lake Superior, the remains of fish (mostly suckers) were found to average 35.4 cm (13.9 in) in total length. In the Columbia River estuary, most preyed on by eagles were estimated to measure between 30 and 60 cm (12 and 24 in) in length, and carp flown with (laboriously) were up to 86 cm (34 in) in length. In Neagle Lake, eagles frequently take Northern pike, up to 80 cm (31 in) long. They can take fish up to at least twice their own weight, such as large salmon, carp, or muskellunge (Esox masquinongy), though they are unable to fly away with it. 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.
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. Bald eagles also regularly exploit water turbines which produce battered, stunned or dead fish easily consumed. 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. Once North Pacific salmon die off after spawning, usually local bald eagles eat salmon carcasses almost exclusively. Eagles in Washington 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 during winter.


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. Overall, birds are the most diverse group in the bald eagle's prey spectrum, with 200 prey species recorded.
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. American herring gull (Larus smithsonianus) are the favored avian prey species for eagles living around Lake Superior. Black ducks (Anas rubripes), common eiders (Somateria mollissima), and double-crested cormorants (Phalacrocorax auritus) are also frequently taken in coastal Maine velvet scoter (Melanitta fusca) was dominant prey in San Miguel Island.
Due to easy accessibility and lack of formidable nest defense 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. 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 precipitous population declines, causing concern for seabird conservation. Because of this more extensive predation, some biologist has expressed concern that murres are heading for a "conservation collision" due to heavy eagle predation. 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. If a bald eagle flies close by, waterbirds will often fly away en masse, though in other cases they may seemingly ignore a perched eagle. when the birds fly away from a colony, this exposed their unprotected eggs and nestlings to scavengers such as gulls.
Larger waterbirds are occasionally prey as well, with wintering emperor geese (Chen canagica) and snow geese (C. caerulescens), which gather in large groups, sometimes becoming regular prey. Other large waterbirds hunted at least occasionally by bald eagles have included adults of common murres (Uria aalge), common loons (Gavis immer), great black-backed gulls (Larus marinus), sandhill cranes (Grus canadensis), great blue herons (Ardea herodias), Ross's geese (Anser rossii), Some waterbird prey can exceed the eagle's own weight. Canada geese (Branta canadensis) are occasionally taken, and predation on the largest subspecies (Branta canadensis maxima) has been reported. Adults of tundra swans (Cygnus columbianus) and brown pelicans (Pelecanus occidentalis) are known to killed by bald eagles. Additionally, chicks or fledgling of American white pelicans (Pelecanus erythrorhynchos), trumpeter swans (Cygnus buccinator) and whooping cranes (Grus americana) can be taken by bald eagles, and unsuccessful attacks on adults have been reported.
Bald eagles have been recorded as killing other raptors on occasion. In some cases, these may be attacks of competition or kleptoparasitism on rival species but ended with the consumption of the victim. Nine species each 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). Larger diurnal raptors known to have fallen victim to bald eagles have included red-tailed hawks (Buteo jamaicensis), peregrine falcons (Falco peregrinus), northern goshawks (Accipiter gentilis), ospreys (Pandion haliaetus) and black (Coragyps atratus) and turkey vultures (Cathartes aura).


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.). Bald eagles in Seedskadee National Wildlife Refuge often hunt in pair to catch rabbits and prairie dogs. They can attack and prey on rabbits and hares of nearly any size, from marsh rabbits to white-tailed jackrabbits. In San Luis Valley, white-tailed jackrabbits can be important prey. Additionally, rodents such as montane voles (Microtus montanus), brown rats (Rattus norvegicus), muskrats (Ondatra zibethicus), nutrias (Myocastor coypus), and various squirrels are taken as supplementary prey. Even American porcupines are reportedly attacked and killed.
Where available, seal colonies can provide a lot of food. On Protection Island, Washington, they commonly feed on harbor seal (Phoca vitulina) afterbirths, still-borns and sickly seal pups. Similarly, Bald eagles in Aleska readily prey on sea otter (Enhydra lutris) pups. Small mammalian carnivores can be taken infrequently, such as American martens (Martes pennanti), American minks (Neovison vison), and Island foxes. Larger carnivores such as Arctic foxes (Vulpes lagopus), striped skunks (Mephitis mephitis), raccoons , and domestic cats (Felis catus) can be taken as well. Predation on more formidable species such as North American river otters (Lontra canadensis) and adult male fisher cats (Pekania pennanti) have been reported. Even bobcat (Lynx rufus) has been recorded amongst their prey, It is unknown that the eagles killed or scavenged them. Additional wild mammalian prey include fawns of white-tailed deer and Sitka deer, which can be taken alive by bald eagles and Virginia opossum (Didelphis virginiana), which are mainly taken as roadkills, though predation on a live specimen has been filmed.
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 11 kg (24 lb), by bald eagles but they are much less likely to attack a healthy lamb than a golden eagle and both species prefer native, wild prey and are unlikely to cause any extensive detriment to human livelihoods. 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 60 kg (130 lb), is much larger than any other known prey taken by this species.


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. 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 17.1 cm (3.6 to 6.7 in). Similarly, many turtles were recorded in the diet in the Chesapeake Bay.In Texas, softshell turtles are the most frequently taken prey, and a large number of Barbour's map turtles are taken in Torreya State Park. Other reptilian and amphibian prey includes southern alligator lizards (Elgaria multicarinata), snakes such as garter snakes, and Greater siren (Siren lacertina).
Invertebrates are occasionally taken. In Alaska, eagles feed on sea urchins (Strongylocentrotus sp.), chitons, mussels, and crabs. Other various mollusks such as land snails, abalones, bivalves, periwinkles, blue mussels, squids, and starfishes are taken as well.


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. 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. 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).< 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. 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.
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.
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. Due to this, bald eagles often outnumber golden eagles at attractive food sources. 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. Bald eagles as frequently mobbed by smaller raptors, due to their infrequent but unpredictable tendency to hunt other birds of prey. 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. 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. 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. Healthy adult bald eagles are not preyed upon in the wild and are thus considered apex predators.


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. It is thought that bald eagles mate for life. However, if one member of a pair dies or disappears, the survivor will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates. 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. Usually, a territory defended by a mature pair will be 1 to 2 km (0.62 to 1.24 mi) of waterside habitat.
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 late June to early July. 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 4 m (13 ft) deep, 2.5 m (8.2 ft) across and weigh 1 metric ton (1.1 short tons). One nest in Florida 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). This nest is on record as the largest tree nest ever recorded for any animal. 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. 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.
In Sonora, Mexico, eagles have been observed nesting on top of hecho catcuses (Pachycereus pectin-aboriginum). 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. The eggs 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). Eggs in Alaska averaged 130 g (4.6 oz) in mass, while in Saskatchewan they averaged 114.4 g (4.04 oz). As with their ultimate body size, egg size tends to increase with distance from the equator. 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. Eagles in captivity have been capable of producing up to seven eggs. It is rare for all three chicks to successfully reach the fledgling stage. The oldest chick often bears the advantage of larger size and louder voice, which tends to draw the parents' attention towards it. 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. However, nearly half of 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. 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).
A young eaglet can gain up to 170 g (6.0 oz) a day, the fastest growth rate of any North American bird. 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 up in the air. The young fledge at anywhere from 8 to 14 weeks of age, though will remain close to the nest and 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. For the next four years, immature eagles wander widely in search of food until they attain adult plumage and are eligible to reproduce.
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. The hawk, nicknamed "Spunky" by biologists monitoring the nest, fledged successfully.


The average lifespan of bald eagles in the wild is around 20 years, with the oldest confirmed one having been 38 years of age. In captivity, they often live somewhat longer. In one instance, a captive individual in New York lived for nearly 50 years. As with size, the average lifespan of an eagle population appears to be influenced by its location and access to prey. 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. 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. 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. In this study, 68% of mortality was human-caused. Today, eagle-shooting is believed to be considerably reduced due to the species' protected status. In one case, an adult eagle investigating a peregrine falcon nest for prey items sustained a concussion from a swooping parent peregrine, and ultimately died days later from it. An early natural history video depicting a cougar (Puma concolor) ambushing and killing an immature bald eagle feeding at a rabbit carcass is viewable online, although this film may have been staged.
Most non-human-related mortality involves nestlings or eggs. Around 50% of eagles survive their first year. However, in the Chesapeake Bay area, 100% of 39 radio-tagged nestlings survived to their first year. 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. 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. 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. 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.


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. 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. It is estimated that the early 18th century the bald eagle population was 300,000–500,000, but by the 1950s there were only 412 nesting pairs in the 48 contiguous states of the US.
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 state 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). 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. Leading causes of death in bald eagles include lead pollution, poisoning, collision with motor vehicles, and power-line electrocution.
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. 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. DDT was completely banned in Canada in 1989, though its use had been highly restricted since the late 1970s.
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; 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. 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. 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. 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.
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. It has also been assigned a risk level of least concern category on the IUCN Red List. 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. In some areas, the increase in eagles has led to decreases in other bird populations and the eagles may be considered a pest.


In December 2016, the U.S. Fish and Wildlife Service proposed quadrupling the number of bald eagles that can be killed by the wind electric generation industry without paying a penalty to 4,200 per year.  If issued, the permits would last 30 years, six times the current 5-year permits.


Permits are required to keep bald eagles in captivity in the United States. Permits are primarily issued to public educational institutions, and the eagles which 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 and facilities, as well as workers experienced in the handling and care of eagles. The bald eagle can be long-lived in captivity if well cared for, but does not breed well even under the best conditions.
In Canada and in England a license is required to keep bald eagles for falconry. 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.


The bald eagle is important in various Native American cultures and, as the national bird of the United States, is prominent in seals and logos, coinage, postage stamps, and other items relating to the U.S. federal government.


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. 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. 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. The Pawnee considered eagles as symbols of fertility because their nests are built high off the ground and because they fiercely protect their young. The Choctaw considered the bald eagle, who has direct contact with the upper world of the sun, as a symbol of peace.
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.
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.
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.


The bald eagle is the national bird of the United States of America. The founders of the United States were fond of comparing their new republic with the Roman Republic, in which eagle imagery (usually involving the golden eagle) was prominent. On June 20, 1782, the Continental Congress adopted the design for the Great Seal of the United States, depicting a bald eagle grasping 13 arrows and an olive branch with thirteen leaves with its talons.
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.
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:
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.


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.


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


The white-bellied sea eagle is generally territorial; some birds form permanent pairs that inhabit territories throughout the year, while others are nomadic. The species is monogamous, with pairs remaining together until one bird dies, after which the surviving bird quickly seeks a new mate. This can lead to some nest sites being continuously occupied for many years (one site in Mallacoota was occupied for over fifty years). Immature birds are generally dispersive, with many moving over 50 km (31 mi) away from the area they were raised. One juvenile raised in Cowell, South Australia was reported 3,000 km (1,900 mi) away at Fraser Island in Queensland. A study of the species in Jervis Bay showed increases in the numbers of immature and subadult birds in autumn, although it was unclear whether these were locally fledged or (as was considered more likely) an influx of young birds born and raised elsewhere in Australia. Birds are often seen perched high in a tree, or soaring over waterways and adjacent land. They are most commonly encountered singly or in pairs. Small groups of white-bellied sea eagles sometimes gather if there is a plentiful source of food such as a carcass or fish offal on a ship. Much of the white-bellied sea eagle's behaviour, particularly breeding, remains poorly known.


The African fish eagle (Haliaeetus vocifer) 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: nkwazi in Chewa, aigle pêcheur in French, hungwe in Shona, inkwazi in isiZulu, and ntšhu (pronounced "ntjhu") in Northern Sotho. This species may resemble the bald eagle in appearance; though related, each species occurs on different continents, with the bald eagle being resident in North America.


The African fish eagle is a species placed in the genus Haliaeetus (sea eagles). Its closest relative appears to be the critically endangered Madagascar fish eagle (H. vociferoides). Like all sea eagle species pairs, this one consists of a white-headed species (the African fish eagle) and a tan-headed one (Madagascar fish eagle). These are an ancient lineage of sea eagles, and as such, have dark talons, beaks, and eyes Both species have at least partially white tails even as juveniles. The scientific name is derived from Haliaeetus, New Latin for "sea eagle" (from the Ancient Greek haliaetos), and vocifer is derived from its original genus name, so named by the French naturalist François Levaillant, who called it 'the vociferous one'.


The African fish eagle is a large bird. The female, at 3.2–3.6 kg (7.1–7.9 lb) is larger than the male, at 2.0–2.5 kg (4.4–5.5 lb). This is typical sexual dimorphism in birds of prey. Males usually have wingspans around 2.0 m (6.6 ft), while females have wingspans of 2.4 m (7.9 ft). The body length is 63–75 cm (25–29.5 in). The adult is very distinctive in appearance with a mostly brown body with a white head like the bald eagle and large, powerful, black wings. The head, breast, and tail of African fish eagles are snow white, with the exception of the featherless face, which is yellow. The eyes are dark brown in colour. The hook-shaped beak, ideal for a carnivorous lifestyle, is yellow with a black tip. The plumage of the juvenile is brown in colour, and the eyes are paler compared to the adult. The feet have rough soles and are equipped with powerful talons to enable the eagle to grasp slippery aquatic prey. While this species mainly subsists on fish, it is opportunistic and may take a wider variety of prey such as waterbirds. Its distinctive cry is, for many, evocative of the spirit or essence of Africa. The call, shriller when uttered by males, is a weee-ah, hyo-hyo or a heee-ah, heeah-heeah.


This species is still quite common near freshwater lakes, reservoirs, and rivers, although it can sometimes be found near the coast at the mouths of rivers or lagoons. African fish eagles are indigenous to sub-Saharan Africa, ranging over most of continental Africa south of the Sahara Desert. Several examples of places where they may be resident include the Orange River in South Africa and Namibia, the Okavango Delta in Botswana, and Lake Malawi bordering Malawi, Tanzania, and Mozambique. The African fish eagle is thought to occur in substantial numbers around the locations of Lake Victoria and other large lakes in central Africa, particularly the Rift Valley lakes. This is a generalist species, requiring only open water with sufficient prey and a good perch, as evidenced by the number of habitat types in which this species may be found, including grassland, swamps, marshes, tropical rainforest, fynbos, and even desert-bordering coastlines, such as that of Namibia. The African fish eagle is absent from arid areas with little surface water.


African fish eagles breed during the dry season, when water levels are low. They are believed to mate for life. Pairs often maintain two or more nests, which they frequently reuse. Because nests are reused and built upon over the years, they can grow quite large, some reaching 2.0 m (6.5 ft) across and 1.2 m (3.9 ft) deep. The nests are placed in a large tree and are built mostly of sticks and other pieces of wood.
The female lays one to three eggs, which are primarily white with a few reddish speckles. Incubation is mostly done by the female, but the male incubates when the female leaves to hunt. Incubation lasts for 42 to 45 days before the chicks hatch. Siblicide does not normally occur in this taxon, and the parents often successfully rear two or three chicks. Chicks fledge around 70 to 75 days old. Postfledgling dependence lasts up to three months, whereafter the juveniles become nomadic, and may congregate in groups away from territorial adults. Those that survive their first year have a life expectancy of some 12 to 24 years.


The African fish eagle feeds mainly on fish, which it swoops down upon from a perch in a tree, snatching the prey from the water with its large, clawed talons. The eagle then flies back to its perch to eat its catch. Like other sea eagles, the African fish eagle has structures on its toes called spiricules that allow it to grasp fish and other slippery prey. The osprey, a winter visitor to Africa also has this adaptation. African fish eagles usually catch fish around 200 to 1,000 g (0.44 to 2.20 lb), but fish up to 4,200 g (9.3 lb) can be taken. If it catches a fish too heavy to allow the eagle to sustain flight, it will drop into the water and paddle to the nearest shore with its wings. Mullets and catfishs are common prey, though various fish such as cichlids, tilapias, characins can be also taken. Even African tigerfish (Hydrocynus vittatus) can be preyed upon by fish eagles especially while predating barn swallows (Hirundo rustica) in flight.
It also feeds on birds, especially waterbirds such as ducks, greater and lesser flamingos. Other preys include small turtles and terrapins, baby crocodiles, nile monitors, skinks, frogs, and carrion. Occasionally, it may even take mammalian prey, such as hyrax, monkeys, rats, hares, and dik diks. It has also been observed feeding on domestic fowl (chickens). The African fish eagle is known to steal the catch of other bird species, known as kleptoparasitism. Targeted species are usually large wading birds such as goliath herons and shoebills, which usually hunt large fish and take a long time to handle.


This species is listed as least concern by the IUCN. The estimated population size is about 300,000 individuals with a distribution area of 18,300,000 km².


The whistling kite (Haliastur sphenurus) is a medium-sized diurnal raptor found throughout Australia (including coastal islands), New Caledonia and much of New Guinea (excluding the central mountains and the northwest). Also called the whistling eagle or whistling hawk, it is named for its loud whistling call, which it often gives in flight.  Some authorities put this species in the genus Milvus, despite marked differences in behaviour, voice and plumage between this species and other members of that genus.


The whistling kite ranges in size from 50 to 60 cm (20 to 24 in), with a wingspan between 123 to 146 cm (4 ft 0 in to 4 ft 9 in).  Weights range from 380 to 1,050 g (0.84 to 2.31 lb) an average of 600 to 750 g (1.32 to 1.65 lb) for males and 750 to 1,000 g (1.65 to 2.20 lb) for females.  As with most raptors, females are larger and heavier than males; though there is considerable overlap between the sexes, females can be up to 21% larger and 42% heavier.  Southern birds are also larger than those found in the tropics. Male and female plumages are the same.  Adult birds are a pale buff on the head, breast and tail, with browner wings and black flight feathers.  Immature birds are a heavily streaked reddish-brown with prominent pale spots on the wings.  Throughout their lives, whistling kites have bone-colored legs and feet, which are unfeathered.  Overall, the whistling kite looks small-headed and long-tailed, with wingtips falling well short of the tail tip when the bird is perched.  Though its legs are short, the bird walks easily on the ground. Whistling kites soar on slightly bowed wings, with their long flight feathers often well-splayed.  The striking pattern on their underwings is distinctive.


This is a noisy species, calling regularly in flight and while perched—even while at the nest. Its most common call is a clear descending whistle, often followed (less often preceded) by a rapid series of rising notes. Intriguingly, field research carried out in Taunton Scientific National Park, Central Queensland by Fiona Randall from the University of Edinburgh, Scotland has shown that spotted bowerbirds (Chlamydera maculata) in that park regularly mimic the calls of whistling kites, with the frequency of mimicry increasing as the breeding season progresses. The function of this mimicry is unknown.


A species of open or lightly wooded areas, whistling kites are typically found near water, at elevations ranging from sea level to 1400 meters.  Though the species as a whole is generally sedentary, some Australian birds are known to be nomadic, wandering to coastal areas in northern Australia during the dry season;  some south Australian birds migrate to the south in the autumn.  There is some evidence that the species is declining locally in southern Australia due to the drainage of wetlands and an accompanying decline in food supplies.


Whistling kites tend to be found singly or in pairs, but sometimes gather in larger groups, particularly during nomadic movements, at roost sites and at sources of plentiful food.


Whistling kites are truly catholic in their tastes, taking small mammals, birds, fish, reptiles, amphibians, crustaceans, insects and carrion.  Those in Australia tend to take primarily live prey (except in the winter, when they subsist largely on carrion), while those in New Guinea are principally scavengers.  Most food items are taken either from the ground or from the water surface, though insects are sometimes hawked directly from the air.  Whistling kites are also known to pirate meals from ibises and herons and from other raptors, and to force large waterbirds to regurgitate their catches.  They regularly patrol roads in search of roadkill, and hover over the edges of grass fires in search of potential prey fleeing the flames. When food is scarce they will almost entirely rely on finding carrion.


The whistling kite's nest is a bulky platform made of sticks and lined with green leaves, placed in an upright fork of a tall tree—often a eucalypt or pine in a riparian area.   Pairs often re-use the same nest year after year, annually adding material until the platform becomes quite large. Females normally lay 2–3 bluish-white eggs, which are sometimes covered with reddish-brown blotches; clutches of 1–4 eggs have been recorded. Eggs are incubated for 35–40 days, and the species is reported to have a 60% hatching success. Chicks, which are covered with cream- or buff-colored down feathers, spend 44–54 days in the nest before fledging, and are dependent on their parents for a further 6–8 weeks after leaving the nest. In Australia, the birds generally breed between June and October in the south, and between February and May in the north, though they may nest at any time after rain providing there are adequate food supplies.


Halictus ligatus was originally described by Thomas Say in 1837. The genus name Halictus refers to a group of sweat bees of the family Halictidae and order Hymenoptera known for their eusocial behavior and underground nesting. Within Halictidae, the subfamily Halictinae is unique for the substantial diversity in social behavior exhibited among species or within species, such as in H. rubicundus. For instance, species of this subfamily may exhibit either solitary nesting, communal nesting, cleptoparasitism, social parasitism, or primitive eusociality similar to H. ligatus.


The appearance of H. ligatus individuals closely resembles other members of the genus Halictus. These individuals are easily differentiated from those of the closely related Lasioglossum by the presence of their pale fasciae hair bands on the posterior margins of the metasomal terga. In addition, the species is predominantly black or brown-black and lacks the faint metallic tints found in bees of the Seladonia subgenus. Moreover, species of Halictus are generally larger than species of Seladonia which are typically under 7 mm long.
H. ligatus females are easily distinguished from other females by a postero-ventral genal tooth. In addition, the males are easily distinguished from other males by the presence of long suberect hairs on the second and third metasomal sterna.


For H. ligatus, similar to other eusocial halictids, the differences in reproductive strategies among females correlate with distinctions in body size and appearance. For instance foundresses, or queens, tend to be large-bodied females in order to maximize energetic reserves, thereby enabling them to overwinter, establish nests, and reproduce independently. On the contrary, helpers tend to be smaller-bodied daughters with undeveloped ovaries.


Halictus ligatus is one of the most abundant and readily identifiable bees in North America, encompassing a wide range of aridities and altitudes. The species can be found in North American for about 50 degrees north latitude, south to the West Indies and Colombia. H. ligatus is also located in temperate areas of the Atlantic to the Pacific, including the southern Gulf of Mexico and southern Canada  This vast range of distribution contributes to local distinctions in behavior, colony cycle, and colony demographic as a result of variation in environmental pressures.


The nests of H. ligatus occur either in rotting wood or within the ground. They have diverse ways of setting up ground nests which can include small cells, scattered cells, and clusters of cells depending on the size of the colony. Nests inside rotting wood are usually irregular in shape due to the constraints of their medium.  The area around the cells is usually uncovered and the cells are lined with a waxy substance from the Dufour's gland of the bee. which is used to protect developing bees.


In north temperate regions, H, ligatus has an annual colony cycle similar to that which is found in almost all other halictines, or social sweat bees, during which the cold winter ensures several months of complete inactivity during which only young gynes survive. Following this period, these individuals undergo a burst of nest initiation in the spring and produce workers during the summer before switching to male and gyne production in the late summer and autumn. In this context, "gynes" are defined as females that are unworn and have no ovarian development. Gynes will overwinter and later become foundresses by initiating nests in the spring. As a result, bees collected towards the end of the colony cycle display a larger proportion of males and young gynes than earlier samples.
However, in the extreme south of Florida, H. ligatus is continuously brooded and multivoltine; having overlapping colony cycles with one complete cycle lasting for up to a few months, with the inclusion of an option break in activity in areas with a pronounced dry season.  In addition, individuals in this region experience markedly reduced reproductive division of labor as compared to those who participate in the annual colony cycle.  As a result, bees collected towards the end of this colony cycle display an increase in the proportion of newly emerged gynes, an increase in the proportion of female bees that are mated, an increase in the proportion of males, and a morphological caste differentiation indicating that the gynes are larger than the worker bees.


The vast range of distribution contributes to the variations in behavior and dominance hierarchy observed for individuals of the species living in different environments. For instance studies indicate that annual variation in local weather conditions actually directly influences the demography of these sweat bee colonies, thereby indirectly influencing the nature of social interactions among adult females. In fact, habitats experiencing adverse conditions caused by excessive rainfall resulted in poor brood survival, production of fewer workers, and queen-dominated oviposition. Under more favorable conditions such as warm weather, it was found that colony and brood survival was high, large numbers of workers were produced, and workers were responsible for a larger proportion of eggs laid in the reproductive brood. These distinctions in environment may also affect colony size and decrease eusociality. For instance, in southern areas with long nesting seasons where there are a large number of workers per nest, queen control of worker behavior is less effective than in northern areas with shorter nesting seasons where there are fewer workers per nest.


Female sweat bees of H. ligatus exhibit a wide range of reproductive roles, ranging from typically foundress (or queen-like) to typically worker-like. Nests founded in the spring are mostly haplometrotic or founded by a single queen. A few others, around 12%, are pleometrotic or founded by anywhere from 2 to 6 queens. In these pleiometric associations, dominant foundresses behave in a manner similar to haplometrotic queens while subordinates behave like mid-summer workers.
The choice of reproductive role available to a particular female is generally dictated by several important factors at the time of emergence including social milieu of the nest, body size and fat stores at eclosion, and time of year. For instance, females that emerge in mid-summer that are small, have few or no fat stores, and whose nesting includes a larger queen tend to develop as workers who assist their mothers to raise the second, reproductive brood. On the contrary, females that emerge in late summer that are large and have large fat stores are destined to mate and become queens of their own nests in the following spring.


Typical queens in single foundress colonies exhibit behaviors consisting of solitary nest excavation and spring provisioning for the brood followed by queen-type behavior after the mid-summer emergency of workers. These behaviors include ceasing to forage and instead overlooking the workers of the colony. For colonies in which there exist multiple foundress associations, subordinates continue to forage while their social role more closely resembles that of a mid-summer worker as opposed to a haplometrotic spring queen.


In established nests, workers may directly compete with the queen as well as each other for oviposition, and attempt to lay their own eggs though many workers forgo their own reproduction and provision for others' offspring. However, many other workers lay eggs, thereby raising their own offspring in addition to the queen's. In fact, around half of H. ligatus workers are inseminated and actually capable of producing diploid eggs.


The life history and development time for H. ligatus is comparable with that of H. confusus as well as other Halictus species. The development from egg to adult takes around 36 days in the spring when the soil temperatures are low. However, this development in the summer takes only around 28 days as a result of higher soil temperatures.
The life cycle of H. ligatus consists of two main stages: the overwintering and the active stage. The nest, which occurs within burrows in the ground or rotting wood, begins to become active and bees awake from their hibernal diapause in late April to early June, but will not leave their overwintering burrows until late June. Hibernal diapause is a delayed development that occurs in many insects where there is no growth and feeding of larvae, embryonic and pupal development stops, and mating, reproduction, and egg development of adults does not occur.  Nests are established by a single female bee, who has mated and laid eggs last spring, called the foundress, but there have also been instances where multiple bees may start a nest together.  The foundress will forage for several weeks in early June to provide for the first brood which will be composed of mostly of small females, who become workers, and a few males  Once the workers have emerged, they start to forage and will produce their own reproductive brood that is composed of both males and females. The females in this group are called gynes and they are those that overwinter and enter hibernal diapause to become foundresses the following spring  and after they emerge they mate and dig an overwintering tunnel beneath the one they came from and enter diapause.
H. ligatus are mass provisoners meaning that they will construct a mass of pollen and nectar which will be the sole source of food for the developing larva and the larvae will not pupate until they have consumed the entire pollen mass. Daughters of the first brood may become non-reproductive helpers that either forage or stay in their natal nest to assist the queen in raising the next brood, or will reproduce in their natal nest, will find other nests to reproduce in, or enter diapause early and become a foundress in the next spring. In most cases, when there are larger colonies,  queens will produce the eggs that become males wheres workers will produce gyne destined eggs. Within a single foundress colony the average relatedness is 0.5, implying that the queens will use equal amounts of sperm from two males that are not related. This is only able to occur because workers have maintained their ancestral abilities of being able to breed independently, which has direct fitness benefits for the worker through reproduction and indirect fitness benefits by being able to help relatives. This is why, in larger colonies, workers are more likely to reproduce as it increases the genetic diversity of the nest allowing for a better proliferation of the species.


Weather pattern differences from year to year and other environmental factors effect the ways in which H. ligatus develop. Changes in weather patterns can result in significant body size variation in all castes of the colony. H. ligatus are ectothermic organisms meaning that both food availability and temperature have significant effects on development and body size. At higher temperatures, ectothermic insects develop faster causing them to move from one larval stage to the next at a faster pace and then spend less time feeding as juveniles. Due to this, those insects will be smaller when they enter their adult stage compared to those who had more time eat as juveniles.


Halictus poeyi, or Poey's furrow bee, is a species of sweat bee in the family Halictidae.


Halictus rubicundus, the orange-legged furrow bee, is a species of sweat bee found throughout the Northern Hemisphere.  H. rubicundus was introduced into North America from the Old World during one of two main invasions of Halictus subgenera. These invasions likely occurred via the Bering land bridge at times of low sea level during the Pleistocene epoch.
The species exhibits different social behaviors depending on climate: it is a solitary species in high elevations or latitudes where the season is short, but eusocial in other areas. Often, solitary and eusocial colonies appear simultaneously in the same population. These sweat bees are extensively studied for their variability in social behavior, which has become a model for social plasticity. This variability has contributed to an understanding of evolution of social behavior.


Halictus rubicundus is a species of Hymenoptera in the bee family Halictidae, more commonly known as sweat bees. This common name comes from their frequent attraction to perspiration. This species exhibits polymorphic social behavior that varies with environmental conditions, and other species of the family Halictidae are thought to have similar variability in sociality.


Many members of the family Halictidae are metallic in appearance but Halictus rubicundus are not metallic. Females are about 1 cm in body length and brown in color, with fine white bands across the apices of the abdominal segments, and rusty-orange legs. The males are more slender, with longer antennae and yellow markings on the face and legs; they can be distinguished from males of similar species by the absence of an apical hair band on the terminal abdominal segment. In social populations, females of the first brood, mostly workers, can be recognized because they are typically slightly smaller than the foundresses.


H. rubicundus has one of the widest natural distributions of any bee species, occurring throughout the temperate regions of the Holarctic region. It is believed that differences in climate across this vast range actually contribute to variation in their social behavior. Those living in more northern geographic locations or higher elevations are often more solitary in behavior than those in southern areas or lower elevations. This difference is widely studied, as it provides insight into the evolutionary transition from solitary to social behavior. Nests are haplometrotic, meaning that they are founded by single females. Social populations typically are found in warmer regions, such as Kansas, while solitary populations nest in cooler regions, such as Colorado, Scotland and Alaska. In intermediate regions, such as New York and southern Ontario, both social and solitary behavior can be found in different nests of the same population. The strictly solitary phenotype is expressed as a response to colder environments because the active season is not long enough to produce two broods.


Both solitary and eusocial types of the species typically excavate nest burrows in southward facing slopes in isolated areas, consisting of sand or soil. This slope maximizes the heat absorption from the sun, making the nest warmer. The nests with a favorable slope were thought to increase foraging efficiency of adults and development of larvae with a stable thermal environment.
Stones or areas of vegetation are usually found near nest entrances, likely because of the heating properties of these objects. For each offspring, a females constructs a small underground chamber (a "brood cell"), into which she deposits several loads of pollen mixed with nectar, which is then formed into a ball; a single egg is laid upon this pollen mass, and then the brood cell is sealed. The female repeats the process with other brood cells, going progressively deeper into the soil. A higher temperature increases the rate at which the larvae develop to maturity, as thermal regulation is important for the development of both the eggs and the larvae.
The nests can be up to 120 mm deep, and are constructed in a wide range of soil types. Because social nests produce more offspring than solitary nests, social nests will burrow further into the ground, as the second brood of the social population will extend the burrows downward. Females typically nest in dense aggregations, likely because the nesting females are relatives and demonstrate philopatric behavior.