Birds

Bald eagle

Bald eagle

“American Eagle” redirects here. For other uses, see American Eagle (disambiguation) and Bald Eagle (disambiguation).
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Bald eagle
2010-bald-eagle-kodiak.jpg
An adult bald eagle at Alaska’s Kodiak Island in July 2010.
Conservation status

Least Concern (IUCN 3.1)[1]
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Haliaeetus
Species: H. leucocephalus
Binomial name
Haliaeetus leucocephalus
(Linnaeus, 1766)
Subspecies

H. l. leucocephalus – Southern bald eagle
H. l. washingtoniensis – Northern bald eagle
Distribution H. leucocephalus.png
Bald eagle range
Breeding resident
Breeding summer visitor
Winter visitor
On migration only
Star: accidental records
Synonyms

Falco leucocephalus Linnaeus, 1766

The bald eagle (Haliaeetus leucocephalus, from Greek hali- = sea, aiētos = eagle, leuco- = white, cephalos = head) is a bird of prey found in North America. A sea eagle, it has two known sub-species and forms a species pair with the white-tailed eagle (Haliaeetus albicilla). 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 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.[2] 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 “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 beak is large and hooked. The plumage of the immature is brown.

The bald eagle is both the national bird and national animal of the United States of America. The bald eagle appears on its Seal. In the late 20th century it was on the brink of extirpation in the continental United States. Populations recovered and the species was removed from the U.S. federal 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 Lower 48 States on June 28, 2007.

Description

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.[2] 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.[3] The beak is large and hooked, with a yellow cere.[4] The adult bald eagle is unmistakable in its native range. The closely related African fish eagle (H. vocifer) (from far outside the bald eagle’s range) also has a brown body, white head and tail, but differs from the bald in having a white chest and black tip to the bill.[5]

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.[2][3] Immature bald eagles are distinguishable from the golden eagle (Aquila chrysaetos), the only other very large, non-vulturine 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.[6] Another distinguishing feature of the immature bald eagle over the mature bird is its black, yellow-tipped beak; the mature eagle has a fully yellow beak.

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.[7] However, the golden eagle, averaging 4.18 kg (9.2 lb) and 63 cm (25 in) in wing chord length in its American race (A. c. 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).[5][8] 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 (H. pelagicus), may, rarely, wander to coastal Alaska from Asia.[5]

Bald eagle
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A recording of a bald eagle at Yellowstone National Park
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The bald eagle has a body length of 70–102 cm (28–40 in). Typical wingspan is between 1.8 and 2.3 m (5.9 and 7.5 ft) and mass is normally between 3 and 6.3 kg (6.6 and 13.9 lb).[5] Females are about 25% larger than males, averaging 5.6 kg (12 lb), and against the males’ average weight of 4.1 kg (9.0 lb).[2][9][10][11] The size of the bird varies by location and generally corresponds with Bergmann’s rule, since 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 (6.2 ft) in wingspan, smaller than their northern counterparts.[12] The largest eagles are from Alaska, where large females may weigh up to 7.5 kg (17 lb) and span 2.44 m (8.0 ft) across the wings.[4][13] A survey of adult weights in Alaska showed that females weighed on average 6.3 kg (14 lb) and males weighed 4.3 kg (9.5 lb).[14] 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).[5][15] 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).[15][16]

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.[5][6]
Taxonomy

The bald eagle placed in the genus Haliaeetus (sea eagles) which gets both its common and specific scientific names from the distinctive appearance of the adult’s head. Bald in the English name is derived from the word piebald, and refers to the white head and tail feathers and their contrast with the darker body.[17] The scientific name is derived from Haliaeetus, New Latin for “sea eagle” (from the Ancient Greek haliaetos), and leucocephalus, Latinized Ancient Greek for “white head,” from λευκος leukos (“white”) and κεφαλη kephale (“head”).[18][19]

The bald eagle was one of the many species originally described by Linnaeus in his 18th century work Systema Naturae, under the name Falco leucocephalus.[20]

There are two recognized subspecies of bald eagle:[2][21]

H. l. leucocephalus (Linnaeus, 1766) is the nominate subspecies. It is found in the southern United States and Baja California.[22]
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.[2][22]

The bald eagle forms a species pair with the Eurasian white-tailed eagle. 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.[23]
Range

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.[24] Today, they are much more common (almost attaining their peak numbers pre-colonization in North America), and nest in every continental state and province in the United States and Canada.[25]

Bald eagles will 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.[26]

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.[27]
Habitat
Juvenile with salmon, Katmai National Park

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.[28]

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.[29] 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.[30] 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.[31][32] Trees used for nesting in the Greater Yellowstone area average 27 m (89 ft) high.[33] 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.[28] 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.[7]

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.[34]

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.[30] 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.[7] In Southeast Alaska, Sitka spruce (Picea sitchensis) provided 78% of the nesting trees used by eagles, followed by hemlocks (Tsuga) at 20%.[29] Increasingly, eagles nest in man-made reservoirs stocked with fish.[30]
With freshly caught fish in Kodiak

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.[28] However, bald eagles will occasionally venture into 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.[35][36] 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.[37]

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.[7][29]
Behavior
Head details

The bald eagle is a powerful flier, and soars on thermal convection currents. It reaches speeds of 56–70 km/h (35–43 mph) when gliding and flapping, and about 48 km/h (30 mph) while carrying fish.[38] Its dive speed is between 120–160 km/h (75–99 mph), though it seldom dives vertically.[39] It is partially migratory, depending on location. If its territory has access to open water, it remains there year-round, but if the body of water freezes during the winter, making it impossible to obtain food, it migrates to the south or to the coast. A number of populations are subject to post-breeding dispersal, mainly in juveniles; Florida eagles, for example, will disperse northwards in the summer.[40] The bald eagle selects migration routes which take advantage of thermals, updrafts, and food resources. During migration, it may ascend in a thermal and then glide down, or may ascend in updrafts created by the wind against a cliff or other terrain. Migration generally takes place during the daytime, usually between the local hours of 8:00 a.m. and 6:00 p.m., when thermals are produced by the sun.[3]
Diet and feeding
Bald eagle feeding on catfish and other various fishes. Painted by John James Audubon.

The bald eagle is an opportunistic carnivore with the capacity to predate a great variety of prey. Throughout their range, fish often comprise the majority of the eagle’s diet.[41] 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%.[42] In Southeast Alaska, fish comprise approximately 66% of the year-around diet of bald eagles and 78% of the prey brought to the nest by the parents.[43] Eagles living in the Columbia River Estuary in Oregon were found to rely on fish for 90% of their dietary intake.[44] In the Pacific Northwest, spawning trout and salmon provide most of the bald eagles’ diet from late summer throughout fall.[45] Southeast Alaskan eagles largely predate pink salmon (Oncorhynchus gorbuscha), coho salmon (O. kisutch) and, more locally, sockeye salmon (O. nerka), with chinook salmon (O. tshawytscha), due to their large size (12 to 18 kg (26 to 40 lb) average adult size) probably being taken only as carrion.[43] 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).[43] 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%).[44] Eagles living in the Chesapeake Bay in Maryland were found to subsist largely on American gizzard shad (Dorosoma cepedianum), threadfin shad (D. petenense) and white bass (Morone chrysops).[46] Floridian eagles have been reported to predate catfish, mostly prevalently the brown bullhead (Ameiurus nebulosus) and any species in the Ictalurus genus as well as mullet, trout, needlefish, and eels.[7][30][47] Wintering eagles on the Platte River in Nebraska preyed mainly on American gizzard shads and common carp.[48] From observation in the Columbia River, 58% of the fish were caught directly by the predating eagle, 24% were scavenged as carcasses and 18% were pirated away from other animals.[44]

Even eagles living in relatively arid regions still typically rely primarily on fish as prey. In Sonora, Mexico and Arizona, 77% and over 73%, respectively, of prey remains at the nests were from fish, largely various catfish and rainbow trout (Oncorhynchus mykiss). 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.[49] At nests around Lake Superior, the remains of fish (mostly suckers) were found to average 35.4 cm (13.9 in) in total length.[50] In the Columbia River estuary, most predated 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.[44]

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.[46] Bald eagles also regularly exploit water turbines which produce battered, stunned or dead fish easily consumed.[51] 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.[43] 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.[42]

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.[44][52] Exceptionally, in the Greater Yellowstone area, birds were eaten as regularly as fish year-around, with both prey groups comprising 43% of the studied dietary intake.[33] Preferred avian prey includes grebes, alcids, ducks, gulls, coots, herons, egrets, and geese.[53] 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.[7][44] American herring gull (Larus smithsonianus) are the favored avian prey species for eagles living around Lake Superior.[50] Larger waterbirds are occasionally predated as well, with wintering emperor geese (Chen canagica) and snow geese (C. caerulescens), which gather in large groups, sometimes becoming regular prey.[15][54] Other large waterbirds hunted at least occasionally by bald eagles have included common loons (Gavis immer),[55] great black-backed gulls (Larus marinus),[56] sandhill cranes (Grus canadensis),[57] great blue herons (Ardea herodias),[42] Canada geese (Branta canadensis),[46] brown pelicans (Pelecanus occidentalis),[30] and fledging American white pelicans (P. erythrorhynchos).[58] Colony nesting seabirds, such as alcids, storm petrels, cormorants, northern gannets (Morus bassanus), terns and gulls, may be especially vulnerable to predation. Due to easy accessibility and lack of formidable nest defense by such species, bald eagles are capable of predating such seabirds at all ages, from eggs to mature adults, and can effectively cull large portions of a colony.[59]

Along some portions of the North Pacific coastline, bald eagles which had historically predated 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 precipitious population declines, causing concern for seabird conservation.[60] Because of this more extensive predation, some biologist have expressed concern that murres are heading for a “conservation collision” due to heavy eagle predation.[59] 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.[61] 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. If the said birds are on a colony, this exposed their unprotected eggs and nestlings to scavengers such as gulls.[59] Bird prey may occasionally be attacked in flight, with prey up to the size of Canada geese attacked and killed in mid-air.[53] Unprecedented photographs of a bald eagle unsuccessfully attempting to predate a much larger adult trumpeter swan (Cygnus buccinator) in mid-flight were taken recently.[62] While adults often actively predate waterbirds, congregated wintering waterfowl are frequently exploited for carcasses to scavenge by immature eagles in harsh winter weather.[63] 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. Raptorial birds reported to have be hunted by these eagles have included large adults of species such as great horned owls (Bubo virginianus),[64][citation needed] red-tailed hawks (Buteo jamaicensis),[65] ospreys (Pandion haliaetus)[66] and black (Coragyps atratus) and turkey vultures (Cathartes aura).[67]

Mammalian prey includes rabbits, hares, ground squirrels, raccoons (Procyon lotor), muskrats (Ondatra zibethicus), beavers (Castor canadensis), and deer fawns. Newborn, dead, sickly or already injured mammals are often targeted. However, more formidable prey such as adult raccoons and sub-adult beavers are sometimes attacked. In the Chesapeake Bay area, bald eagles are reportedly the main natural predators of raccoons.[68][69] Where available, seal colonies can provide much food. On Protection Island, Washington, commonly feed on harbor seal (Phoca vitulina) afterbirths, still-borns and sickly seal pups.[70] On San Juan Island in Washington, introduced European rabbits (Oryctolagus cuniculus), mainly those killed by auto accidents, comprise nearly 60% of the dietary intake of eagles.[71] In landlocked areas of North America, wintering bald eagles may become habitual predators of medium-sized mammals that occur in colonies or local concentrations, such prairie dogs (Cynomys) and jackrabbits (Lepus).[7][72] Together with the golden eagle, bald eagles are occasionally accused of predating livestock, especially sheep (Ovis aries). There are a handful of proven cases of lamb predation, some of 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.[73] 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.[74]

Supplemental prey are readily taken given the opportunity. In some areas reptiles may become regular prey, especially warm areas such as Florida where reptile diversity is high. Turtles are perhaps the most regularly hunted type of reptile.[7] 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).[75] Snakes are also taken occasionally, especially partially aquatic ones, as are amphibians and crustaceans (largely crayfish and crabs).[30][44]

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.[38] Bald eagles have powerful talons and have been recorded flying with a 6.8 kg (15 lb) mule deer (Odocoileus hemionus) fawn.[76] This feat is the record for the heaviest load carrying ever verified for a flying bird.[77] 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.[78] 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, 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.[30][54] On numerous occasions, when large prey such as 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.[15] 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.[30] 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.[4][79][80] 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 which 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.[15]

Unlike some other eagle species, bald eagles rarely take on evasive or dangerous prey on their own. The species mainly target prey which is much smaller than themselves, with most live fish caught weighing 1 to 3 kg (2.2 to 6.6 lb) and most waterbirds predated weighing 0.2 to 2.7 kg (0.44 to 5.95 lb).[43][54][81] They attain much their food as carrion or via a practice known as kleptoparasitism, where they steal prey away from other predators. Due to their dietary habits, bald eagles are frequently viewed in a negative light by humans.[7] 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.[82][83] 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.[15] Bald eagles also may sometimes feed on subsistence scavenged or stolen from campsites and picnics, as well as garbage dumps (dump usage is habitual mainly in Alaska).[84]

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.[84] Occasionally, coyotes, bobcats (Lynx rufus) and domestic dogs (Canis lupus familiaris) can displace eagles from carrion, usually less confident immature birds, as has been recorded in Maine.[85] 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).[8] 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.[15] 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.[8][25] Due to this, bald eagles often outnumber golden eagles at attractive food sources.[8] 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.[86] Similarly, both eagle species have been recorded, via video-monitoring, to feed on gut pills and carcasses of white-tailed deer (Odocoileus virginianus) in remote forest clearings in the eastern Appalachian Mountains without apparent conflict.[8] 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.[15][87] 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.[88][89] When they approach scavengers like dogs, gulls or vultures at carrion sites, they often aggressively attack them and try to force them to disgorge their food.[30] Healthy adult bald eagles are not preyed on in the wild and are thus considered apex predators.[90]
Reproduction

Bald eagles are sexually mature at four or five years of age. When they are old enough to breed, they often return to the area where they were born. It is thought that bald eagles mate for life. However, if one member of a pair dies or disappears, the other will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates.[91] Bald eagle courtship involves elaborate, spectacular calls and flight displays. The flight includes swoops, chases, and cartwheels, in which they fly high, lock talons, and free fall, separating just before hitting the ground.[42][92] Usually, a territory defended by a mature pair will be 1 to 2 km (0.62 to 1.24 mi) of waterside habitat.[7]
Mating

Compared to most other raptors which mostly nest in April or May, bald eagles are early breeders: nest building or reinforcing is often by mid-February, egg laying is often late February (sometimes during deep snow in the North), and incubation is usually mid-March and early May. Eggs hatch from mid April to early May, and the young fledge late June to early July.[7] 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);[2] 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).[93] This nest is on record as the largest tree nest ever recorded for any animal.[94] Usually nests are used for under five years or so, 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.[30] The nest is built out 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.[84] In Sonora, Mexico, eagles have been observed nesting on top of Hecho catcuses (Pachycereus pectinaboriginum).[95] 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.[7] 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 cm (19 to 25 in).[38][42] Eggs in Alaska averaged 130 g (4.6 oz) in mass, while in Saskatchewan they averaged 114.4 g (4.04 oz).[96][97] As with their ultimate body size, egg size tends to increase further away from the Equator.[42] 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.[98] Eagles in captivity have been capable of producing up to seven eggs.[99] it is rare for all three chicks to successfully reach the fledging stage. The oldest chick often bear the advantage of larger size and louder voice, which tends to draw the parents attention towards them.[7] Occasionally, as is recorded in many large raptorial birds, the oldest sibling sometimes attacks and kills their younger sibling(s), especially early in the nesting period when their sizes are most different.[7] However, nearly half of known bald eagle produce two fledgings species (more rarely three), unlike in some other “eagle” species such as some in the Aquila genus, in which a second fledging is typically observed in less than 20% of nests despite two eggs being typically laid.[14] Both the male and female take turns incubating the eggs, but the female does most of the incubation. 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).[7] A young eaglet can gain up to 170 g (6.0 oz) a day, the fastest growth rate of any North American bird.[30] 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.[30] 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.[97] For the next four years, immature eagles wander widely in search of food until they attain adult plumage and are eligible to reproduce.[100]
Longevity and mortality
Newly fledged juvenile

The average lifespan of bald eagles in the wild is around 20 years, with the oldest confirmed one having been 28 years of age.[4] 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.[101] 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.[8] In Prince William Sound in Alaska, adults had an annual survival rate of 88% even after the Exxon Valdez oil spill adversely effected eagles in the area.[102] 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.[103] In this study, 68% of mortality was human-caused.[103] Today eagle-shooting is believed to be considerably reduced due to the species protected status.[104] 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.[105] An early natural history video depicts 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.[106]

Most non-human-related mortality involves nestlings or eggs. Around 50% of eagles survive their first year.[100] However, in the Chesapeake Bay area, 100% of 39 radio-tagged nestlings survived to their first year.[107] Occasionally, nestling or egg fatalities are due to nest collapses, starvation, sibling aggression or inclement weather. Another significant cause of egg and nestling mortality is predation. These have been verified to be predated by large gulls, corvids (including ravens, crows and magpies), Wolverines (Gulo gulo), hawks, owls, eagles, bobcats (Lynx rufus), American black bears (Ursus americanus) and raccoons.[96][108][109][110][111][112][113] 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.[14] 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.[84] 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.[114]
Relationship with humans
Population decline and recovery

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.[115] 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 the bird’s calcium metabolism, making the bird either sterile or unable to lay healthy eggs. Female eagles laid eggs that were too brittle to withstand the weight of a brooding adult, making it nearly impossible for the eggs to hatch.[24] It is estimated that in the early 18th century, the bald eagle population was 300,000–500,000,[116] 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).[117] Later illegal shooting was described as “the leading cause of direct mortality in both adult and immature bald eagles,” according to a 1978 report in the Endangered Species Technical Bulletin. In 1984, the National Wildlife Federation listed hunting, power-line electrocution, and collisions in flight as the leading causes of eagle deaths. Bald eagles have also been killed by oil, lead, and mercury pollution, and by human and predator intrusion at nests.[118]

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 1940 bald eagle Protection Act in the U.S., which protected the bald eagle and the golden eagle, prohibited 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.[119] DDT was completely banned in Canada in 1989, though its use had been highly restricted since the late 1970s.[120]
First-year

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;[2] 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.[2] Obtaining a precise count of bald eagles population is extremely difficult. The most recent data submitted by individual states was in 2006, when 9789 breeding pairs were reported.[121] 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.[25]

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.[122] It has also been assigned a risk level of Least Concern category on the IUCN Red List.[1] 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.[4]
In captivity

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 which 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. Bald eagles cannot legally be kept for falconry in the United States. As a rule, the bald eagle is a poor choice for public shows, being timid, prone to becoming highly stressed, and unpredictable in nature. Native American tribes can obtain a “Native American Religious Use” permit to keep non-releasable eagles as well. They use their naturally molted feathers for religious and cultural ceremonies. The bald eagle can be long-lived in captivity if well cared for, but does not breed well even under the best conditions.[123] In Canada, a license is required to keep bald eagles for falconry.[124]
Cultural significance
In Skagit Valley, Washington, United States

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.
Role in Native American culture

The bald eagle is a sacred bird in some North American cultures, and its feathers, like those of the golden eagle, are central to many religious and spiritual customs among Native Americans. Eagles are considered spiritual messengers between gods and humans by some cultures.[125] 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. 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.[126] The Pawnee considered eagles as symbols of fertility because their nests are built high off the ground and because they fiercely protect their young.[127] The Choctaw considered the bald eagle, who has direct contact with the upper world of the sun, as a symbol of peace.[128]
Staff at the National Eagle Repository processing a bald eagle.

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.[129]

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.[130][131]

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.[132]
National bird of the United States
Seal of the President of the United States

The bald eagle is the national bird of the United States of America.[133] 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 still-current design for the Great Seal of the United States including a bald eagle grasping 13 arrows and a 13-leaf olive branch with its talons.[134][135][136]

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.[137]

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:[4]

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.[138]

http://en.wikipedia.org/wiki/Bald_eagle

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Birds

Green bee-eater

Green bee-eater
From Wikipedia, the free encyclopedia
Not to be confused with Little bee-eater.
Green bee-eater
Green Bee-eater (Merops orientalis) in Tirunelveli.jpg
ssp. orientalis
Conservation status

Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Coraciiformes
Family: Meropidae
Genus: Merops
Species: M. orientalis
Binomial name
Merops orientalis
Latham, 1802
Synonyms

Merops viridis Neumann, 1910

The green bee-eater (Merops orientalis) (sometimes little green bee-eater) is a near passerine bird in the bee-eater family. It is resident but prone to seasonal movements and is found widely distributed across sub-Saharan Africa from Senegal and the Gambia to Ethiopia, the Nile valley, western Arabia and Asia through India to Vietnam.[2] They are mainly insect eaters and they are found in grassland, thin scrub and forest often quite far from water. Several regional plumage variations are known and several subspecies have been named.

Description
Subspecies muscatensis from the UAE

Like other bee-eaters, this species is a richly coloured, slender bird. It is about 9 inches (16–18 cm) long with about 2 inches made up by the elongated central tail-feathers. The sexes are not visually distinguishable. The entire plumage is bright green and tinged with blue especially on the chin and throat. The crown and upper back are tinged with golden rufous. The flight feathers are rufous washed with green and tipped with blackish. A fine black line runs in front of and behind the eye. The iris is crimson and the bill is black while the legs are dark grey. The feet are weak with the three toes joined at the base.[3] Southeast Asian birds have rufous crown and face, and green underparts, whereas Arabian beludschicus has a green crown, blue face and bluish underparts. The wings are green and the beak is black. The elongated tail feathers are absent in juveniles. Sexes are alike.[2]

The calls is a nasal trill tree-tree-tree-tree, usually given in flight.[3]
Taxonomy
Race orientalis from Coimbatore, India

Several populations have been designated as subspecies:[4]

viridissimus is found from Senegal to northern Ethiopia (has more green on the throat, crown and nape with long streamers)
cleopatra from the Nile Valley to northern Sudan
flavoviridis from northern Chad to Sudan
muscatensis on the Arabian plateau (more yellowish green with narrow gorget on throat)
cyanophrys found in Israel and the Arabian region (includes meccanus)
beludschicus(=biludschicus[5]) Iran to Pakistan (paler colours with a blue throat)[6]
orientalis in India and Sri Lanka (has head and neck tinged with rufous)
ferrugeiceps (=birmanus) in northeastern India, Myanmar, Thailand and Vietnam (has rufous crown, name and mantle)
ceylonicus in Sri Lanka has the nape and hindneck with more pronounced golden brown sheen[7] often included within the nominate race

A study of species within the genus Merops based on plumage characteristics found that most of the subspecies of orientalis grouping together with the most similar species being Merops leschenaulti and subspecies ferrugeiceps appeared closer to that group.[8]

Leucistic individuals have been noted.[9]
Distribution and habitat
Green bee-eater perched on a branch

This is an abundant and fairly tame bird, familiar throughout its range. It is a bird which breeds in open country with bushes. In Africa and Arabia it is found in arid areas, but is more diverse in its habitats further east. This species often hunts from low perches, maybe only a metre or less high. It readily makes use of fence wires and electric wires. Unlike some other bee-eaters, they can be found well away from water.[4]

They are mostly see in the plains but can sometimes be found up to 5000 or 6000 feet in the Himalayas. They are resident in the lowlands of South Asia but some populations move seasonally but the patterns are not clear,[3] moving away to drier regions in the rainy season and to warmer regions in winter.[4] In parts of Pakistan, they are summer visitors.[10]
Behaviour and ecology
File:Green Bee-eater – Merops orientalis.ogvPlay media
Green bee-eater (Merops orientalis) on a branch of tree. Captured in Okanda, Sri Lanka.
Little Green bee eater (Merops orientalis) in Dubai.

Like other species in the genus, bee-eaters predominantly eat insects, especially bees, wasps and ants, which are caught in the air by sorties from an open perch. Before swallowing prey, a bee-eater removes stings and breaks the exoskeleton of the prey by repeatedly thrashing it on the perch. Migration is not known but they make seasonal movements in response to rainfall.[2] These birds are somewhat sluggish in the mornings and may be found huddled next to each other on wires sometimes with their bills tucked in their backs well after sunrise. They sand-bathe more frequently than other bee-eater species and will sometimes bathe in water by dipping into water in flight.[4] They are usually seen in small groups and often roost communally in large numbers (200-300). The birds move excitedly at the roost site and call loudly, often explosively dispersing before settling back to the roost tree.[11] The little green bee-eater is also becoming common in urban and sub-urban neighborhoods, and has been observed perching on television antennae, only to launch into a brief, zig-zag flight formation to catch an insect, then return to the same perch and consume the meal. This behaviour is generally observed between the hours of 7:00 and 8:00am, and after 4:00pm.
Sand bathing.

The breeding season is from March to June. Unlike many bee-eaters, these are often solitary nesters, making a tunnel in a sandy bank. The breeding pairs are often joined by helpers.[12][13] They nest in hollows in vertical mud banks. The nest tunnel that they construct can run as much as 5 feet long and the 3-5 eggs are laid on the bare ground in the cavity at the end of the tunnel. The eggs are very spherical and glossy white.[3] Clutch size varies with rainfall and insect food density. Both sexes incubate. The eggs hatch asynchronously with an incubation period of about 14 days and the chicks grow fledge in 3 to 4 weeks and in the fledging stage show a reduction in body weight.[14][15]

A study suggested that green bee-eaters may be capable of interpreting the behaviour of human observers. They showed an ability to predict whether a human at a particular location would be capable of spotting the nest entrance and then behaved appropriately to avoid giving away the nest location. The ability to look at a situation from another’s point of view was previously believed to be possessed only by primates.[16][17]

Riverside habitats were found to support high populations in southern India (157 birds per square kilometre) dropping off too 101 per km² in agricultural areas and 43-58 per square km near human habitations.[18]

They feed on flying insects and can sometimes be nuisance to bee-keepers.[19] The preferred prey was mostly beetles followed by hymenopterans. Orthopterans appear to be avoided.[20] They are sometimes known to take crabs.[21] Like most other birds they regurgitate the hard parts of their prey as pellets.[22]
Race orientalis with a dragonfly in Hyderabad, India.

An endoparasitic nematode (Torquatoides balanocephala) sometimes infects their gizzard.[23]

http://en.wikipedia.org/wiki/Green_bee-eater

Birds

Snow goose

Snow goose

This article is about species of goose. For the novella by Paul Gallico, see The Snow Goose. For the Camel album, see Music Inspired by The Snow Goose (album).
Snow goose
Chen caerulescens 32398.JPG
C. c. caerulescens white morph
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Subfamily: Anserinae
Tribe: Anserini
Genus: Chen
Species: C. caerulescens
Binomial name
Chen caerulescens
(Linnaeus, 1758)
Subspecies
Chen caerulescens map.svg
Snow goose range:     Breeding range     Wintering range
Synonyms
Anser caerulescens (but see text)

The snow goose (Chen caerulescens), also known as the blue goose, is a North American species of goose. Its name derives from the typically white plumage. The genus of this bird is disputed. The American Ornithologists’ Union and BirdLife International place this species and the other “white geese” in the Chen genus,[2] while other authorities follow the traditional treatment of placing these species in the “gray goose” genus Anser.[3][4]

This goose breeds north of the timberline in Greenland, Canada, Alaska, and the northeastern tip of Siberia, and spends winters in warm parts of North America from southwestern British Columbia through parts of the United States to Mexico. They fly as far south as Texas and Mexico during winter, and return to nest on the Arctic tundra each spring. [5] It is a rare vagrant to Europe, but a frequent escape from collections and an occasional feral breeder. Snow geese are visitors to the British Isles where they are seen regularly among flocks of barnacle, Brent and Greenland white-fronted geese. There is also a feral population in Scotland from which many vagrant birds in Britain seem to derive.

In Central America, vagrants are frequently encountered during winter.[6]

Description

C. c. caerulescens blue morph

C. c. atlanticus, spring migration, blue morphs in foreground, Alexandria, Ontario

The snow goose has two color plumage morphs, white (snow) or gray/blue (blue), thus the common description as “snows” and “blues.” White-morph birds are white except for black wing tips, but blue-morph geese have bluish-grey plumage replacing the white except on the head, neck and tail tip. The immature blue phase is drab or slate-gray with little to no white on the head, neck, or belly. Both snow and blue phases have rose-red feet and legs, and pink bills with black tomia (“cutting edges”), giving them a black “grin patch.” The colors are not as bright on the feet, legs, and bill of immature birds. The head can be stained rusty-brown from minerals in the soil where they feed. They are very vocal and can often be heard from more than a mile away.

White- and blue-morph birds interbreed and the offspring may be of either morph. These two colors of geese were once thought to be separate species; since they interbreed and are found together throughout their ranges, they are now considered two color phases of the same species. The color phases are genetically controlled. The dark phase results from a single dominant gene and the white phase is homozygous recessive. When choosing a mate, young birds will most often select a mate that resembles their parents’ coloring. If the birds were hatched into a mixed pair, they will mate with either color phase.

The species is divided into two subspecies on the basis of size and geography. Size overlap has caused some to question the division.[5] The smaller subspecies, the lesser snow goose (C. c. caerulescens), lives from central northern Canada to the Bering Straits area. The lesser snow goose stands 64 to 79 cm (25 to 31 in) tall and weighs 2.05 to 2.7 kg (4.5 to 6.0 lb). The larger subspecies, the greater snow goose (C. c. atlanticus), nests in northeastern Canada. It averages about 3.2 kg (7.1 lb) and 79 cm (31 in), but can weigh up to 4.5 kg (9.9 lb). The wingspan for both subspecies ranges from 135 to 165 cm (53 to 65 in). Blue-morph birds are rare among the greater snow geese and among eastern populations of the Lesser.

Breeding

Greater snow geese in flight

Snow geese (Anser caerulescens)

Long-term pair bonds are usually formed in the second year, although breeding does not usually start until the third year. Females are strongly philopatric, meaning they will return to the place they hatched to breed.

Snow geese often nest in colonies. Nesting usually begins at the end of May or during the first few days of June, depending on snow conditions. The female selects a nest site and builds the nest on an area of high ground. The nest is a shallow depression lined with plant material and may be reused from year to year. After the female lays the first of 3 to 5 eggs, she lines the nest with down. The female incubates for 22 to 25 days, and the young leave the nest within a few hours of hatching.

The young feed themselves, but are protected by both parents. After 42 to 50 days they can fly, but they remain with their family until they are 2 to 3 years old.

Where snow geese and Ross’s geese breed together, as at La Pérouse, they hybridize at times, and hybrids are fertile. Rare hybrids with the greater white-fronted goose, Canada goose, and cackling goose have been observed.[5]

Population

The breeding population of the lesser snow goose exceeds 5 million birds, an increase of more than 300% since the mid-1970s. The population is increasing at a rate of more than 5% per year. Non-breeding geese (juveniles or adults that fail to nest successfully) are not included in this estimate, so the total number of geese is even higher. Lesser Snow Goose population indices are the highest they have been since population records have been kept, and evidence suggests that large breeding populations are spreading to previously untouched sections of the Hudson Bay coastline.

Migration

Snow geese in a corn field on Fir Island, Washington in the Skagit River delta

Snow geese breed from late May to mid August, but they leave their nesting areas and spend more than half the year on their migration to-and-from warmer wintering areas. During spring migration, large flocks of snow geese fly very high along narrow corridors, more than 3000 miles from traditional wintering areas to the tundra.

The lesser snow goose travels through the Central Flyway, across some of the richest farmland in America. Traditionally, the geese wintered in coastal marsh areas where they used their short but very strong bills to dig the roots of marsh grasses for dinner. The first transition was to rice fields, where the geese could graze on weeds and eat the grain left behind by the combine. A decade later the geese had mastered field feeding and had diversified into wheat, corn, sorghum and practically any other field grain they encountered. The geese had also begun to graze in fall-seeded grain fields, especially winter wheat. Snow Geese now feed in grain fields as soon as they reach the prairies in September, and they continue to use agricultural fields until they leave the prairies in April and May on their way to Arctic breeding areas.

Many biologists think the shift in winter feeding has led to the over-abundance of geese. Winter may be the time of year that sets the upper limit to goose populations. Now, the abundance of waste agricultural grain has provided snow geese with excellent forage and has improved the survival of wintering geese. The national wildlife refuges bought to protect habitat also help to increase survival. Therefore, more geese are returning to the Arctic to breed each spring. Those returning geese are in much better physical condition than was the case when geese did not use agricultural grain but foraged in marshland.

Ecology

Wintering snow geese on Fir Island, Washington

Outside of the nesting season, they usually feed in flocks. In winter, snow geese feed on left-over grain in fields. They migrate in large flocks, often visiting traditional stopover habitats in spectacular numbers. Snow geese frequently travel and feed alongside greater white-fronted geese; in contrast, the two tend to avoid travelling and feeding alongside Canada geese, which are often heavier birds.[citation needed]

The population of greater snow geese was in decline at the beginning of the 20th century, but has now recovered to sustainable levels. Snow geese in North America have increased to the point where the tundra breeding areas in the Arctic and the saltmarsh wintering grounds are both becoming severely degraded,[7] and this affects other species using the same habitat.

Major nest predators include Arctic foxes and skuas.[8] The biggest threat occurs during the first couple of weeks after the eggs are laid and then after hatching. The eggs and young chicks are vulnerable to these predators, but adults are generally safe. They have been seen nesting near snowy owl nests, which is likely a solution to predation. Their nesting success was much lower when Snowy Owls were absent, leading scientists to believe that the owls, since they are predatory, were capable of keeping competing predators away from the nests. A similar association as with the owls has been noted between geese and rough-legged hawks.[8] Additional predators at the nest have reportedly included wolves, coyotes and all three North American bear species.[9][10] Few predators regularly prey on snow geese outside of the nesting season, but bald eagles (as well as possibly golden eagles) will readily attack wintering geese.[10]

http://en.wikipedia.org/wiki/Snow_goose

Birds

Tufted titmouse

Tufted titmouse

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Adult singing
Conservation status

Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neognathae
Superorder: Neoaves
Order: Passeriformes
Suborder: Passeri
Infraorder: Passerida
Family: Paridae
Genus: Baeolophus
Species: B. bicolor
Binomial name
Baeolophus bicolor
(Linnaeus, 1766)
Combined range of tufted titmouse and black-crested titmouse

The tufted titmouse (Baeolophus bicolor) is a small songbird from North America, a species in the tit and chickadee family (Paridae). The black-crested titmouse, found from central and southern Texas southwards, was included as a subspecies but is now considered a separate species B. atricristatus.

These birds have grey upperparts and white underparts with a white face, a grey crest, a dark forehead and a short stout bill; they have rust-coloured flanks. The song is usually described as a whistled peter-peter-peter. They make a variety of different sounds, most having a similar tone quality.

The habitat is deciduous and mixed woods as well as gardens, parks and shrubland[2] in the eastern United States; they barely range into southeastern Canada in the Great Lakes region. They are all-year residents in the area effectively circumscribed by the Great Plains, the Great Lakes, the Gulf of Mexico and the Atlantic Ocean. The range is expanding northwards, possibly due to increased availability of winter food at bird feeders. The birds are nowadays resident all year even in rural Ohio where there are few bird feeders, while it was noted around 1905 that many birds from these areas migrated south in winter.[2][3]

They forage actively on branches, sometimes on the ground, mainly eating insects, especially caterpillars, but also seeds, nuts and berries. They will store food for later use. They tend to be curious about their human neighbors and can sometimes be spotted on window ledges peering into the windows to watch what’s going on inside. They are more shy when seen at bird feeders; their normal pattern there is to scout the feeder from the cover of trees or bushes, fly to the feeder, take a seed, and fly back to cover to eat it.

Tufted titmice nest in a hole in a tree, either a natural cavity, a man-made nest box, or sometimes an old woodpecker nest. They line the nest with soft materials, sometimes plucking hair from a live animal such as a dog. If they find shed snake skin, they will try to incorporate pieces of it in their nest.[4] Their eggs are under an inch long and are white or cream-colored with brownish or purplish spots. Sometimes, a bird born the year before remains to help its parents raise the next year’s young. The pair may remain together and defend their territory year-round. These birds are permanent residents and often join small mixed flocks in winter. In rare cases, many birds may flock together to rest in a log or tree; some may even suffocate because so many birds are crowded inside of one cavity.

http://en.wikipedia.org/wiki/Tufted_titmouse

Birds

Piping plover

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Piping plover

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Charadriidae
Genus: Charadrius
Species: C. melodus
Binomial name
Charadrius melodus
(Ord, 1824)
Subspecies
C. m. circumcinctus
C. m. melodus

The piping plover (Charadrius melodus) is a small sand-colored, sparrow-sized shorebird that nests and feeds along coastal sand and gravel beaches in North America. The adult has yellow-orange legs, a black band across the forehead from eye to eye, and a black ring around the neck. This chest band is usually thicker in males during the breeding season, and it’s the only reliable way to tell the sexes apart. The bird is difficult to see when it is standing still, as it blends well with open, sandy beach habitats. It typically runs in short spurts and stops.

There are 2 subspecies of piping plovers: the eastern population is known as Charadrius melodus melodus and the mid-west population is known as C. m. circumcinctus. The bird’s name is derived from its plaintive bell-like whistles which are often heard before the bird is visible.

Total population is currently estimated at about 6,510 individuals. A preliminary estimate showed 3,350 birds in 2003 on the Atlantic Coast alone, 52% of the total.[2] The population has been increasing since 1999.

Their breeding habitat includes beaches or sand flats on the Atlantic coast, the shores of the Great Lakes, and in the mid-west of Canada and the United States. They nest on sandy or gravel beaches or shoals. These shorebirds forage for food on beaches, usually by sight, moving across the beaches in short bursts. Generally, piping plovers will forage for food around the high tide wrack zone and along the water’s edge. They eat mainly insects, marine worms, and crustaceans.

On the Atlantic coast, Cape May, New Jersey, USA
The piping plover is a stout bird with a large rounded head, a short thick neck, and a stubby bill. It is a sand-colored, dull gray/khaki, sparrow-sized shorebird. The adult has yellow-orange legs, a black band across the forehead from eye to eye, and a black ring around the neck during the breeding season. During nonbreeding season, the black bands become less pronounced.[3] Its bill is orange with a black tip. It ranges from 15–19 cm (5.9–7.5 in) in length, with a wingspan of 35–41 cm (14–16 in) and a mass of 42–64 g (1.5–2.3 oz).[4]

SubspeciesEdit
Two subspecies are recognized, including nominate C. m. melodus of the Atlantic Coast and C. m. circumcinctus of the Great Plains. On average, circumcinctus is darker overall with more contrastingly dark cheeks and lores. Breeding male circumcinctus shows more extensive black on forehead and bill-base and more often shows complete breast-bands. Some overlap exists.

VocalizationsEdit
Flight call is a soft, whistled peep peep given by standing and flying birds. Its frequently heard alarm call is a soft pee-werp, which the second syllable lower pitched.

HabitatEdit
The piping plover lives the majority of its life on open sandy beaches or rocky shores, often in high, dry sections away from water. They can be found on the Atlantic Coast of the U.S. and Canada on the ocean or bay beaches and on the Great Lakes shores. It builds its nests higher on the shore near beach grass and other objects. It is very rare to see a piping plover anywhere outside of sand or rocky beaches/shores while not migrating.

Migration and breedingEdit
Piping plover chick at 2 days.
Piping plovers migrate north in the summer and winter to the south on the Gulf of Mexico, the southern Atlantic coast of the United States and the Caribbean. They begin migrating north beginning in mid-March. Their breeding grounds extend from southern Newfoundland south to the northern parts of South Carolina.[5] They begin mating and nesting on the beach in mid-April.

Males will begin claiming territories and pairing up in late March. When pairs are formed, the male begins digging out several scrapes (nests) along the high shore near the beach-grass line. The males also perform elaborate courtship ceremonies, including stone tossing and courtship flights featuring repeated dives.[3] Scrapes, small depressions in the sand dug by kicking the sand, are often in the same area that least terns choose to colonize. Females will sit and evaluate the scrapes, then choose a good scrape and decorate the nest with shells and debris to camouflage it. Once a scrape is seen as sufficient, the female will allow the male to copulate with her. The male begins a mating ritual of standing upright and “marching” towards the female, puffing himself up and quickly stomping his legs. If the female had seen the scrape as adequate, she will allow the male to stand on her back and copulation occurs within a few minutes.

Most first-time nest attempts in each breeding season are 4-egg nests which appear as early as mid-to-late April. Females lay one egg every other day. Second, third and sometimes fourth nesting attempts may have only three or two eggs. Incubation of the nest is shared by both the male and the female. Incubation is generally 27 days and eggs usually all hatch on the same day.

After chicks hatch, they are able to feed within hours. The adults’ role is then to protect them from the elements by brooding them. They also alert them to any danger. Like many other species of plovers, adult piping plovers will often feign a “broken wing display”, drawing attention to themselves and away from the chicks when a predator may be threatening the chicks’ safety. The broken wing display is also used during the nesting period to distract predators from the nest.[3] A major defense mechanism of the chicks is their ability to blend in with the sand. It takes about 30 days before chicks achieve flight capability. They must be able to fly at least 50 yd (46 m) before they can be considered fledglings.

To protect the nests from predators during incubation, many conservationists use exclosures, such as round turkey-wire cages with screened tops. These allow the adults to move in and out but stop predators from getting to the eggs. After the chicks hatch, many areas will put up snow fencing to restrict driving and pets for the safety of the chicks. Threats to nests include crows, cats, raccoons, and foxes, among others. Exclosures are not always used, as they occasionally draw more attention to the nest than would occur without the exclosure. Natural hazards to eggs or chicks include storms, high winds, and abnormal high tides; human disturbances can cause the abandonment of nests and chicks as well. It is best to stay away from any bird that appears distressed to prevent any unintended consequences.

Piping plover chick with band at two weeks.
Migration south begins in August for some adults and fledglings, and by mid-September most piping plovers have headed south for winter.

BehaviorEdit
Parent and chick on the Atlantic coast, Cape May, New Jersey, USA
Inconspicuous birds of dry sandy beaches, plovers breed in open sand, gravel, or shell-strewn beaches and alkali flats. Each nest site is typically near small clumps of grass, drift, or other windbreak. In winter, these birds prefer sand beaches and mudflats. Migrants are seldom seen inland, but occasionally show up at lake shores, river bars, or alkali flats. Individuals forage visually in typical plover fashion, employing a run-stop-scan technique. Plovers capture prey by leaning forward and picking at surfaces; they also employ a “foot-tremble” feeding method, causing prey to move and become more conspicuous. Feeding by day and night, they eat a wide variety of aquatic marine worms, insects, mollusks, and crustaceans. Seldom found in large numbers except at a few favored wintering or staging sites where numbers sometimes reach 100 or more, plovers are more typically seen in pairs or in groups of 3 or 4. When approached, they more often run than fly.[6] Plovers are very aggressive when nesting.[citation needed]

StatusEdit
The piping plover is globally threatened and endangered; it is uncommon and local within its range, and has been listed by the United States as “endangered” in the Great Lakes region and “threatened” in the remainder of its breeding range.[7] While it is federally threatened, the piping plover has been listed as state endangered in Illinois, Indiana, Maine, Michigan, Minnesota, Nebraska, New Hampshire, New York, New Jersey, Ohio, Pennsylvania, and Wisconsin.

In eastern Canada, the piping plover is found only on coastal beaches. In 1985, it was declared an endangered species by the Committee on the Status of Endangered Wildlife in Canada.[8] A large population in Ontario has disappeared entirely.[9] In 2008, however, piping plover nests were found at Wasaga Beach and near Sauble Beach, Ontario, along the Ontario Great Lakes shores.[10] There is also some evidence of nesting at other sites in Ontario.[11][12]

Historical and current conservationEdit
Area closed within Cape Henlopen State Park, Delaware, where piping plovers are known to nest

Piping plover protected nesting area on Cavendish Beach, P.E.I.
In the 19th century and early 20th century, the piping plover was utilized for its feathers, as were many other birds at the time, as decorations for women’s hats. These decorations, called plumes, became a symbol of high society, especially those from larger rare birds. This practice led to its initial population decline. The Migratory Bird Treaty Act of 1918 helped the population recover through the 1930s.[13] The second decline in the piping plover’s population and range has been attributed to increased development, shoreline stabilization efforts,[14] habitat loss and human activity near nesting sites in the decades following World War II.[13] The Great Lakes populations eventually shrank to only around two dozen.[9]

Critical nesting habitats are now being protected to help the population during its breeding season. Populations have seen significant increases since the protection programs began, but the species remains in serious danger. Current conservation strategies include identification and preservation of known nesting sites; public education; limiting or preventing pedestrian and/or off-road vehicle (ORV) traffic near nests and hatched chicks; limiting predation of free-ranging cats, dogs and other pets on breeding pairs, eggs and chicks;[15] and removal of foxes, raccoons, skunks, and other predators.[16]

In coastal areas such as Plymouth,[17] Cape Cod, Long Island, Sandy Hook,[18] Cape Henlopen State Park in Delaware, North Manitou Island in Lake Michigan, and most recently, Cape Hatteras National Seashore on the Outer Banks of North Carolina, beach access to pedestrians and ORVs has been limited to protect piping plovers and their chicks at critical times of the breeding season.

http://en.m.wikipedia.org/wiki/Piping_plover

Art, Birds

Emperor penguins

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Emperor penguins
Emperors are the largest of all penguins—an average bird stands some 45 inches (115 centimeters) tall. These flightless animals live on the Antarctic ice and in the frigid surrounding waters.

Penguins employ physiological adaptations and cooperative behaviors in order to deal with an incredibly harsh environment, where wind chills can reach -76°F (-60°C).

They huddle together to escape wind and conserve warmth. Individuals take turns moving to the group’s protected and relatively toasty interior. Once a penguin has warmed a bit it will move to the perimeter of the group so that others can enjoy protection from the icy elements.

Emperor penguins spend the long winter on the open ice—and even breed during this harsh season. Females lay a single egg and then promptly leave it behind. They undertake an extended hunting trip that lasts some two months! Depending on the extent of the ice pack, females may need to travel some 50 miles (80 kilometers) just to reach the open ocean, where they will feed on fish, squid, and krill. At sea, emperor penguins can dive to 1,850 feet (565 meters)—deeper than any other bird—and stay under for more than 20 minutes.

Male emperors keep the newly laid eggs warm, but they do not sit on them, as many other birds do. Males stand and protect their eggs from the elements by balancing them on their feet and covering them with feathered skin known as a brood pouch. During this two-month bout of babysitting the males eat nothing and are at the mercy of the Antarctic elements.

When female penguins return to the breeding site, they bring a belly full of food that they regurgitate for the newly hatched chicks. Meanwhile, their duty done, male emperors take to the sea in search of food for themselves.

Mothers care for their young chicks and protect them with the warmth of their own brood pouches. Outside of this warm cocoon, a chick could die in just a few minutes. In December, Antarctic summer, the pack ice begins to break up and open water appears near the breeding site, just as young emperor penguins are ready to swim and fish on their own.

http://animals.nationalgeographic.com/animals/birds/emperor-penguin/

Birds

Eastern bluebird

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Eastern Bluebird
Sialia sialis ORDER: PASSERIFORMES FAMILY: TURDIDAE
IUCN Conservation Status: Least Concern
Similar SpeciesRelated SpeciesGo to:

Most of the country drives during an eastern North American summer will turn up a few Eastern Bluebirds sitting on telephone wires or perched atop a nest box, calling out in a short, wavering voice or abruptly dropping to the ground after an insect. Marvelous birds to capture in your binoculars, male Eastern Bluebirds are a brilliant royal blue on the back and head, and warm red-brown on the breast. Blue tinges in the wings and tail give the grayer females an elegant look.

http://www.allaboutbirds.org/guide/Eastern_Bluebird/lifehistory