165-570: Falco pygargus Daudin, 1800 (nec Linnaeus) Falco ossifragus Shaw, 1809 (nec Linnaeus) 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
330-653: 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
495-672: A lammergeier might have killed Aeschylus by accident. Many stories of Brazilian indigenous peoples speak about children mauled by Uiruuetê, the Harpy Eagle in Tupi language . Various large raptors like golden eagles are reported attacking human beings, but its unclear if they intend to eat them or if they have ever been successful in killing one. Some fossil evidence indicates large birds of prey occasionally preyed on prehistoric hominids. The Taung Child , an early human found in Africa,
660-472: 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
825-869: A bald eagle flies close by, waterbirds will often fly away en masse, though they may seemingly ignore a perched eagle in other cases. when the birds fly away from a colony, this exposes their unprotected eggs and nestlings to scavengers such as gulls . While they usually target small to medium-sized seabirds, larger seabirds such as great black-backed gulls ( Larus marinus ) and northern gannets ( Morus bassanus ) and brown pelicans ( Pelecanus occidentalis ) of all ages can successfully be taken by bald eagles. Similarly, large waterbirds are occasionally killed. Geese such as wintering emperor geese ( Chen canagica ) and snow geese ( C. caerulescens ), which gather in large groups, sometimes becoming regular prey. Smaller Ross's geese ( Anser rossii ) are also taken, as well as large-sized Canada geese ( Branta canadensis ). Predation on
990-716: 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
1155-542: A bald eagle was observed carrying 6.8 kg (15 lb) mule deer ( Odocoileus hemionus ) fawn. Additionally, Virginia opossums ( Didelphis virginiana ) can be preyed upon. Still, predation events are rare due to their nocturnal habits. 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. Still, they are much less likely to attack
1320-501: A bird's lifetime. Activational hormones occur during puberty and adulthood and serve to 'activate' certain behaviors when appropriate, such as territoriality during breeding season. Organizational hormones occur only during a critical period early in development, either just before or just after hatching in most birds, and determine patterns of behavior for the rest of the bird's life. Such behavioral differences can cause disproportionate sensitivities to anthropogenic pressures. Females of
1485-414: 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 ),
1650-430: 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. 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
1815-454: A distance or during flight, strong feet with sharp talons for grasping or killing prey, and powerful, curved beaks for tearing off flesh. Although predatory birds primarily hunt live prey, many species (such as fish eagles , vultures and condors ) also scavenge and eat carrion . Although the term "bird of prey" could theoretically be taken to include all birds that actively hunt and eat other animals, ornithologists typically use
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#17327797418481980-459: A diverse array of sexually dimorphic traits. Aggressive utility traits such as "battle" teeth and blunt heads reinforced as battering rams are used as weapons in aggressive interactions between rivals. Passive displays such as ornamental feathering or song-calling have also evolved mainly through sexual selection. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection . The opposite of dimorphism
2145-467: A great deal of data is required. Dimorphisms can also be the product of intrasexual selection between males and females. It appears that both sexes of the species play a role in the sexual dimorphism within raptors; females tend to compete with other females to find good places to nest and attract males, and males competing with other males for adequate hunting ground so they appear as the most healthy mate. It has also been proposed that sexual dimorphism
2310-428: A healthy lamb than a golden eagle. 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
2475-529: 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
2640-553: A large role in the changing of sex by the fish. It is often seen that a fish will change its sex when there is a lack of a dominant male within the social hierarchy. The females that change sex are often those who attain and preserve an initial size advantage early in life. In either case, females which change sex to males are larger and often prove to be a good example of dimorphism. In other cases with fish, males will go through noticeable changes in body size, and females will go through morphological changes that can only be seen inside of
2805-465: A larger image to be projected onto the retina. The visual acuity of some large raptors such as eagles and Old World vultures are the highest known among vertebrates; the wedge-tailed eagle has twice the visual acuity of a typical human and six times that of the common ostrich , the vertebrate with the largest eyes. There are two regions in the retina, called the deep and shallow fovea, that are specialized for acute vision. These regions contain
2970-1011: A less bright or less exaggerated color during the off-breeding season. This occurs because the species is more focused on survival than on reproduction, causing a shift into a less ornate state. Consequently, sexual dimorphism has important ramifications for conservation. However, sexual dimorphism is not only found in birds and is thus important to the conservation of many animals. Such differences in form and behavior can lead to sexual segregation , defined as sex differences in space and resource use. Most sexual segregation research has been done on ungulates, but such research extends to bats , kangaroos , and birds. Sex-specific conservation plans have even been suggested for species with pronounced sexual segregation. The term sesquimorphism (the Latin numeral prefix sesqui - means one-and-one-half, so halfway between mono - (one) and di - (two)) has been proposed for bird species in which "both sexes have basically
3135-798: 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 Alaska readily prey on sea otter ( Enhydra lutris ) pups. Small to medium-sized terrestrial mammalian carnivores can be taken infrequently. Mustelid including American martens ( Martes pennanti ), American minks ( Neogale vison ), and larger fisher cats ( Pekania pennanti ) are known to be hunted. Foxes are also taken, including Island foxes ( Urocyon littoralis ), Arctic foxes ( Vulpes lagopus ), and grey foxes ( Urocyon cinereoargenteus ). Although fox farmers claimed that bald eagle heavily prey on young and adult free-range Arctic fox,
3300-425: A naturally occurring part of development, for example plumage. In addition, the strong hormonal influence on phenotypic differences suggests that the genetic mechanism and genetic basis of these sexually dimorphic traits may involve transcription factors or cofactors rather than regulatory sequences. Sexual dimorphism may also influence differences in parental investment during times of food scarcity. For example, in
3465-492: A preference for bodies of water with a circumference greater than 11 km (7 mi), and lakes with an area greater than 10 km (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
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#17327797418483630-490: 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
3795-549: 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,
3960-414: A significant role in male reproductive success. Males have a propensity to be larger than females of a comparable age but it is unclear whether the size increase is due to a growth spurt at the time of the sexual transition or due to the history of faster growth in sex changing individuals. Larger males are able to stifle the growth of females and control environmental resources. Social organization plays
4125-407: 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
4290-542: A speciation phenomenon if the variation becomes strongly drastic and favorable towards two different outcomes. Sexual dimorphism is maintained by the counteracting pressures of natural selection and sexual selection. For example, sexual dimorphism in coloration increases the vulnerability of bird species to predation by European sparrowhawks in Denmark. Presumably, increased sexual dimorphism means males are brighter and more conspicuous, leading to increased predation. Moreover,
4455-474: Is Lamprologus callipterus , a type of cichlid fish. In this fish, the males are characterized as being up to 60 times larger than the females. The male's increased size is believed to be advantageous because males collect and defend empty snail shells in each of which a female breeds. Males must be larger and more powerful in order to collect the largest shells. The female's body size must remain small because in order for her to breed, she must lay her eggs inside
4620-543: Is Lasioglossum hemichalceum , which is a species of sweat bee that shows drastic physical dimorphisms between male offspring. Not all dimorphism has to have a drastic difference between the sexes. Andrena agilissima is a mining bee where the females only have a slightly larger head than the males. Weaponry leads to increased fitness by increasing success in male–male competition in many insect species. The beetle horns in Onthophagus taurus are enlarged growths of
4785-627: Is monomorphism , when both biological sexes are phenotypically indistinguishable from each other. Common and easily identified types of dimorphism consist of ornamentation and coloration, though not always apparent. A difference in the coloration of sexes within a given species is called sexual dichromatism, commonly seen in many species of birds and reptiles. Sexual selection leads to exaggerated dimorphic traits that are used predominantly in competition over mates. The increased fitness resulting from ornamentation offsets its cost to produce or maintain, suggesting complex evolutionary implications, but
4950-600: Is a deprecated superorder within Raptores, formerly composed of the orders Falconiformes and Strigiformes. The clade was invalidated after 2012. Falconiformes is now placed in Eufalconimorphae , while Strigiformes is placed in Afroaves . The order Accipitriformes is believed to have originated 44 million years ago when it split from the common ancestor of the secretarybird ( Sagittarius serpentarius ) and
5115-423: Is a good indicator for females because it shows that they are good at obtaining a food supply from which the carotenoid is obtained. There is a positive correlation between the chromas of the tail and breast feathers and body condition. Carotenoids play an important role in immune function for many animals, so carotenoid dependent signals might indicate health. Frogs constitute another conspicuous illustration of
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5280-447: 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. Its dive speed is between 120–160 km/h (75–99 mph), though it seldom dives vertically. Regarding their flying abilities, despite being morphologically less well adapted to faster flight than golden eagles (especially during dives),
5445-407: Is a sexually dimorphic trait. Theropoda It has been hypothesized that male theropods possessed a retractable penis, a feature similar to modern day crocodilians . Crocodilian skeletons were examined to determine whether there is a skeletal component that is distinctive between both sexes, to help provide an insight on the physical disparities between male and female theropods. Findings revealed
5610-729: Is a simplified phylogeny of Telluraves which is the clade where the birds of prey belong to along with passerines and several near-passerine lineages. The orders in bold text are birds of prey orders; this is to show the paraphyly of the group as well as their relationships to other birds. Accipitriformes (hawks, vultures, and relatives) [REDACTED] Strigiformes (owls) [REDACTED] Coraciimorphae (woodpeckers, rollers, hornbills, etc.) [REDACTED] Cariamiformes (seriemas) [REDACTED] Falconiformes (falcons) [REDACTED] Psittacopasserae (parrots and songbirds) [REDACTED] A recent phylogenomic study from Wu et al. (2024) has found an alternative phylogeny for
5775-489: 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
5940-423: Is advantageous to both parties because it avoids damaging the developing fruit and wasting the pollinator's effort on unrewarding visits. In effect, the strategy ensures that pollinators can expect a reward every time they visit an appropriately advertising flower. Females of the aquatic plant Vallisneria americana have floating flowers attached by a long flower stalk that are fertilized if they contact one of
6105-587: Is also displayed by dichromatism. In butterfly genera Bicyclus and Junonia , dimorphic wing patterns evolved due to sex-limited expression, which mediates the intralocus sexual conflict and leads to increased fitness in males. The sexual dichromatic nature of Bicyclus anynana is reflected by female selection on the basis of dorsal UV-reflective eyespot pupils. The common brimstone also displays sexual dichromatism; males have yellow and iridescent wings, while female wings are white and non-iridescent. Naturally selected deviation in protective female coloration
6270-673: Is also seen in frog species like P. bibroni i . Male painted dragon lizards, Ctenophorus pictus . are brightly conspicuous in their breeding coloration, but male colour declines with aging . Male coloration appears to reflect innate anti-oxidation capacity that protects against oxidative DNA damage . Male breeding coloration is likely an indicator to females of the underlying level of oxidative DNA damage (a significant component of aging) in potential mates. Possible mechanisms have been proposed to explain macroevolution of sexual size dimorphism in birds. These include sexual selection, selection for fecundity in females, niche divergence between
6435-615: 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 as 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,
6600-492: Is an order of telluravian birds consisting of the living seriemas and extinct terror birds . Jarvis et al. 2014 suggested including them in the category of birds of prey, and McClure et al. 2019 considered seriemas to be birds of prey. The Peregrine Fund also considers seriemas to be birds of prey. Like most birds of prey, seriemas and terror birds prey on vertebrates . However, seriemas were not traditionally considered birds of prey. There were traditionally classified in
6765-407: Is attained at the age of four to five years. Bald eagles are not bald ; the name derives from an older meaning of the word, "white headed". The adult is mainly brown with a white head and tail. The sexes are identical in plumage , but females are about 25 percent larger than males. The yellow beak is large and hooked. The plumage of the immature is brown. The bald eagle is the national symbol of
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6930-470: Is believed that this is obtained by the ingestion of green Lepidopteran larvae, which contain large amounts of the carotenoids lutein and zeaxanthin . This diet also affects the sexually dimorphic colours in the human-invisible ultraviolet spectrum. Hence, the male birds, although appearing yellow to humans, actually have a violet-tinted plumage that is seen by females. This plumage is thought to be an indicator of male parental abilities. Perhaps this
7095-549: Is believed to have been killed by an eagle-like bird similar to the crowned eagle . The Haast's eagle may have preyed on early humans in New Zealand , and this conclusion would be consistent with Maori folklore . Leptoptilos robustus might have preyed on both Homo floresiensis and anatomically modern humans, and the Malagasy crowned eagle , teratorns , Woodward's eagle and Caracara major are similar in size to
7260-445: Is commonly believed that the dimorphisms found in raptors occur due to sexual selection or environmental factors. In general, hypotheses in favor of ecological factors being the cause for sexual dimorphism in raptors are rejected. This is because the ecological model is less parsimonious , meaning that its explanation is more complex than that of the sexual selection model. Additionally, ecological models are much harder to test because
7425-464: Is derived from the Latin word rapio , meaning "to seize or take by force". The common names for various birds of prey are based on structure, but many of the traditional names do not reflect the evolutionary relationships between the groups. Many of these English language group names originally referred to particular species encountered in Britain . As English-speaking people travelled further,
7590-410: Is displayed in mimetic butterflies. Many arachnid groups exhibit sexual dimorphism, but it is most widely studied in the spiders. In the orb-weaving spider Zygiella x-notata , for example, adult females have a larger body size than adult males. Size dimorphism shows a correlation with sexual cannibalism , which is prominent in spiders (it is also found in insects such as praying mantises ). In
7755-600: 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
7920-687: Is known in ceratopsids, although there is evidence that the more primitive ceratopsian Protoceratops andrewsi possessed sexes that were distinguishable based on frill and nasal prominence size. This is consistent with other known tetrapod groups where midsized animals tend to exhibit markedly more sexual dimorphism than larger ones. However, it has been proposed that these differences can be better explained by intraspecific and ontogenic variation rather than sexual dimorphism. In addition, many sexually dimorphic traits that may have existed in ceratopsians include soft tissue variations such as coloration or dewlaps , which would be unlikely to have been preserved in
8085-411: Is merely the product of disruptive selection , and is merely a stepping stone in the process of speciation, especially if the traits that define gender are independent across a species. Sexual dimorphism can be viewed as something that can accelerate the rate of speciation. In non-predatory birds, males are typically larger than females. However, in birds of prey, the opposite is the case. For instance,
8250-678: Is more prominently selected for in less dimorphic species of spiders, which often selects for larger male size. In the species Maratus volans , the males are known for their characteristic colorful fan which attracts the females during mating. Ray-finned fish are an ancient and diverse class, with the widest degree of sexual dimorphism of any animal class. Fairbairn notes that "females are generally larger than males but males are often larger in species with male–male combat or male paternal care ... [sizes range] from dwarf males to males more than 12 times heavier than females." There are cases where males are substantially larger than females. An example
8415-501: 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
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#17327797418488580-402: Is of a subdued brown coloration. The plumage of the peacock increases its vulnerability to predators because it is a hindrance in flight, and it renders the bird conspicuous in general. Similar examples are manifold, such as in birds of paradise and argus pheasants . Another example of sexual dichromatism is that of nestling blue tits . Males are chromatically more yellow than females. It
8745-683: 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
8910-409: 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 and velvet scoter ( Melanitta fusca )
9075-434: Is seen in the bee species Macrotera portalis in which there is a small-headed morph, capable of flight, and large-headed morph, incapable of flight, for males. Anthidium manicatum also displays male-biased sexual dimorphism. The selection for larger size in males rather than females in this species may have resulted due to their aggressive territorial behavior and subsequent differential mating success. Another example
9240-480: Is selected for, which is seen in the family Araneidae . All Argiope species, including Argiope bruennichi , use this method. Some males evolved ornamentation including binding the female with silk, having proportionally longer legs, modifying the female's web, mating while the female is feeding, or providing a nuptial gift in response to sexual cannibalism. Male body size is not under selection due to cannibalism in all spider species such as Nephila pilipes , but
9405-407: Is strong when the factor of environmental selection is also introduced. Environmental selection may support a smaller chick size if those chicks were born in an area that allowed them to grow to a larger size, even though under normal conditions they would not be able to reach this optimal size for migration. When the environment gives advantages and disadvantages of this sort, the strength of selection
9570-504: Is the dragonet , in which males are considerably larger than females and possess longer fins. Sexual dimorphism also occurs in hermaphroditic fish. These species are known as sequential hermaphrodites . In fish, reproductive histories often include the sex-change from female to male where there is a strong connection between growth, the sex of an individual, and the mating system within which it operates. In protogynous mating systems where males dominate mating with many females, size plays
9735-411: Is weakened and the environmental forces are given greater morphological weight. The sexual dimorphism could also produce a change in timing of migration leading to differences in mating success within the bird population. When the dimorphism produces that large of a variation between the sexes and between the members of the sexes, multiple evolutionary effects can take place. This timing could even lead to
9900-506: 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' status was upgraded from " endangered " to " threatened " in 1995 and removed from the list altogether in 2007. The bald eagle is placed in the genus Haliaeetus ( sea eagles ), and gets both its common and specific scientific names from
10065-936: 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
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#173277974184810230-604: The blue-footed booby , the female chicks grow faster than the males, resulting in booby parents producing the smaller sex, the males, during times of food shortage. This then results in the maximization of parental lifetime reproductive success. In Black-tailed Godwits Limosa limosa limosa females are also the larger sex, and the growth rates of female chicks are more susceptible to limited environmental conditions. Sexual dimorphism may also only appear during mating season; some species of birds only show dimorphic traits in seasonal variation. The males of these species will molt into
10395-523: 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 . Wintering eagles on the Platte River in Nebraska preyed mainly on American gizzard shads and common carp. Bald eagles are also known to eat
10560-557: 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
10725-497: The kestrel is a type of falcon in which males are the primary providers, and the females are responsible for nurturing the young. In this species, the smaller the kestrels are, the less food is needed and thus, they can survive in environments that are harsher. This is particularly true in the male kestrels. It has become more energetically favorable for male kestrels to remain smaller than their female counterparts because smaller males have an agility advantage when it comes to defending
10890-641: The merlin ( Falco columbarius ). The taxonomy of Carl Linnaeus grouped birds (class Aves) into orders, genera, and species, with no formal ranks between genus and order. He placed all birds of prey into a single order, Accipitres , subdividing this into four genera: Vultur (vultures), Falco (eagles, hawks, falcons, etc.), Strix (owls), and Lanius (shrikes). This approach was followed by subsequent authors such as Gmelin , Latham and Turton . Louis Pierre Vieillot used additional ranks: order, tribe, family, genus, species. Birds of prey (order Accipitres) were divided into diurnal and nocturnal tribes;
11055-489: The ovules ). Each pollen grain accordingly may be seen as a male plant in its own right; it produces a sperm cell and is dramatically different from the female plant, the megagametophyte that produces the female gamete. Insects display a wide variety of sexual dimorphism between taxa including size, ornamentation and coloration. The female-biased sexual size dimorphism observed in many taxa evolved despite intense male-male competition for mates. In Osmia rufa , for example,
11220-518: 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
11385-407: The 'fittest' available male. Sexual dimorphism is a product of both genetics and environmental factors. An example of sexual polymorphism determined by environmental conditions exists in the red-backed fairywren . Red-backed fairywren males can be classified into three categories during breeding season : black breeders, brown breeders, and brown auxiliaries. These differences arise in response to
11550-695: 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
11715-471: 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,
11880-716: 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
12045-475: The Haast's eagle, implying that they similarly could pose a threat to a human being. Birds of prey have incredible vision and rely heavily on it for a number of tasks. They utilize their high visual acuity to obtain food, navigate their surroundings, distinguish and flee from predators, mating, nest construction, and much more. They accomplish these tasks with a large eye in relation to their skull, which allows for
12210-489: The accipitrid species. The phylogeny of Accipitriformes is complex and difficult to unravel. Widespread paraphylies were observed in many phylogenetic studies. More recent and detailed studies show similar results. However, according to the findings of a 2014 study, the sister relationship between larger clades of Accipitriformes was well supported (e.g. relationship of Harpagus kites to buzzards and sea eagles and these latter two with Accipiter hawks are sister taxa of
12375-532: 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
12540-453: The bald eagle is considered surprisingly maneuverable in flight. Bald eagles have also been recorded catching up to and then swooping under geese in flight, turning over and thrusting their talons into the other bird's breast. 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
12705-697: The bills of birds of prey shown by hunters. In Britain, kites and buzzards were seen as destroyers of game and killed, for instance in 1684–5 alone as many as 100 kites were killed. Rewards for their killing were also in force in the Netherlands from 1756. From 1705 to 1800, it has been estimated that 624087 birds of prey were killed in a part of Germany that included Hannover, Luneburg, Lauenburg and Bremen with 14125 claws deposited just in 1796–97. Many species also develop lead poisoning after accidental consumption of lead shot when feeding on animals that had been shot by hunters. Lead pellets from direct shooting that
12870-531: The biogeographic realms of the Southern Hemisphere. The appearance of migratory behaviour occurred in the tropics parallel with the range expansion of migratory species to temperate habitats. Similar results of southern origin in other taxonomic groups can be found in the literature. Distribution and biogeographic history highly determine the origin of migration in birds of prey. Based on some comparative analyses, diet breadth also has an effect on
13035-533: The bird's body condition: if they are healthy they will produce more androgens thus becoming black breeders, while less healthy birds produce less androgens and become brown auxiliaries. The reproductive success of the male is thus determined by his success during each year's non-breeding season, causing reproductive success to vary with each year's environmental conditions. Migratory patterns and behaviors also influence sexual dimorphisms. This aspect also stems back to size dimorphism in species. It has been shown that
13200-586: The birds have escaped from also cause reduced fitness and premature deaths. Some evidence supports the contention that the African crowned eagle occasionally views human children as prey, with a witness account of one attack (in which the victim, a seven-year-old boy, survived and the eagle was killed), and the discovery of part of a human child skull in a nest. This would make it the only living bird known to prey on humans, although other birds such as ostriches and cassowaries have killed humans in self-defense and
13365-1001: The body. For example, in sockeye salmon , males develop larger body size at maturity, including an increase in body depth, hump height, and snout length. Females experience minor changes in snout length, but the most noticeable difference is the huge increase in gonad size, which accounts for about 25% of body mass. Sexual selection was observed for female ornamentation in Gobiusculus flavescens , known as two-spotted gobies. Traditional hypotheses suggest that male–male competition drives selection. However, selection for ornamentation within this species suggests that showy female traits can be selected through either female–female competition or male mate choice. Since carotenoid-based ornamentation suggests mate quality, female two-spotted guppies that develop colorful orange bellies during breeding season are considered favorable to males. The males invest heavily in offspring during incubation, which leads to
13530-707: 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 less than 30 cm (12 in), but larger fish between 30 and 60 cm (12 and 24 in) or even exceeding 60 cm (24 in) in length also taken especially during
13695-470: The caudal chevrons of male crocodiles, used to anchor the penis muscles, were significantly larger than those of females. There have been criticisms of these findings, but it remains a subject of debate among advocates and adversaries. Ornithopoda Studies of sexual dimorphism in hadrosaurs have generally centered on the distinctive cranial crests , which likely provided a function in sexual display. A biometric study of 36 skulls found sexual dimorphism
13860-523: The clade containing Aquilinae and Harpiinae). The diurnal birds of prey are formally classified into six families of two different orders (Accipitriformes and Falconiformes). These families were traditionally grouped together in a single order Falconiformes but are now split into two orders, the Falconiformes and Accipitriformes . The Cathartidae are sometimes placed in a separate order Cathartiformes . Formerly, they were sometimes placed in
14025-600: 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. 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
14190-1904: The consumption of the dead victims. Nine species of other accipitrids and owls are known to have been preyed upon by bald eagles. Owl prey species have ranged in size from western screech-owls ( Megascops kennicotti ) to snowy owls ( Bubo scandiacus ). 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 cottontails, jackrabbits and prairie dogs. They can attack and prey on rabbits and hares of nearly any size, from marsh rabbits ( Sylvilagus palustris ) to black and white-tailed jackrabbits ( Lepus californicus & L. townsendii ), and Arctic hares ( Lepus arcticus ). In San Luis Valley , white-tailed jackrabbits can be important prey. Additionally, rodents such as montane voles ( Microtus montanus ), brown rats ( Rattus norvegicus ), and various squirrels are taken as supplementary prey. Larger rodents such as muskrats ( Ondatra zibethicus ), young or small adult nutrias ( Myocastor coypus ) and groundhogs ( Marmota monax ) are also preyed upon. Even American porcupines ( Erethizon dorsatum ) are reportedly attacked and killed. Where available, seal colonies can provide
14355-400: The costs and evolutionary implications vary from species to species. The peafowl constitute conspicuous illustrations of the principle. The ornate plumage of peacocks, as used in the courting display, attracts peahens . At first sight, one might mistake peacocks and peahens for completely different species because of the vibrant colours and the sheer size of the male's plumage; the peahen
14520-654: The degree of preservation. The availability of well-preserved remains is not a probable outcome as a consequence of decomposition and fossilization . Some paleontologists have looked for sexual dimorphism among dinosaurs using statistics and comparison to ecologically or phylogenetically related modern animals. Apatosaurus and Diplodocus Female Apatosaurus and Diplodocus had interconnected caudal vertebrae that allowed them to keep their tails elevated to aid in copulation. Discovering that this fusion occurred in only 50% of Apatosaurus and Diplodocus skeletons and 25% of Camarasaurus skeletons indicated that this
14685-1426: 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 rattlesnakes , 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
14850-523: 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,
15015-516: The distinctive appearance of the adult's head. Bald in the English name is from an older usage meaning "having white on the face or head" rather than "hairless", referring to the white head feathers contrasting with the darker body. The genus name is Neo-Latin : Haliaeetus (from the Ancient Greek : ἁλιάετος , romanized : haliaetos , lit. 'sea eagle'), and
15180-445: 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. It has been estimated that
15345-540: 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
15510-816: The eastern Appalachian Mountains without apparent conflict. Bald eagles are 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
15675-448: The empty shells. If she grows too large, she will not fit in the shells and will be unable to breed. The female's small body size is also likely beneficial to her chances of finding an unoccupied shell. Larger shells, although preferred by females, are often limited in availability. Hence, the female is limited to the growth of the size of the shell and may actually change her growth rate according to shell size availability. In other words,
15840-516: The estrogen pathway. The sexual dimorphism in lizards is generally attributed to the effects of sexual selection, but other mechanisms including ecological divergence and fecundity selection provide alternative explanations. The development of color dimorphism in lizards is induced by hormonal changes at the onset of sexual maturity, as seen in Psamodromus algirus , Sceloporus gadoviae , and S. undulates erythrocheilus . Sexual dimorphism in size
16005-439: The evolution of migratory behaviour in this group, but its relevance needs further investigation. The evolution of migration in animals seems to be a complex and difficult topic with many unanswered questions. A recent study discovered new connections between migration and the ecology, life history of raptors. A brief overview from abstract of the published paper shows that "clutch size and hunting strategies have been proved to be
16170-443: The exhausted anthers after a day or two and perhaps change their colours as well while the pistil matures; specialist pollinators are very much inclined to concentrate on the exact appearance of the flowers they serve, which saves their time and effort and serves the interests of the plant accordingly. Some such plants go even further and change their appearance once fertilized, thereby discouraging further visits from pollinators. This
16335-471: The existing literature combining anatomical, genetic, and behavioural studies showed that, in general, raptors have functional olfactory systems that they are likely to use in a range of different contexts. Birds of prey have been historically persecuted both directly and indirectly. In the Danish Faroe Islands , there were rewards Naebbetold (by royal decree from 1741) given in return for
16500-493: The familiar names were applied to new birds with similar characteristics. Names that have generalised this way include: kite ( Milvus milvus ), sparrowhawk or sparhawk ( Accipiter nisus ), goshawk ( Accipiter gentilis ), kestrel ( Falco tinninculus ), hobby ( Falco subbuteo ), harrier (simplified from "hen-harrier", Circus cyaneus ), buzzard ( Buteo buteo ). Some names have not generalised, and refer to single species (or groups of closely related (sub)species), such as
16665-417: The female is larger/broader than males, with males being 8–10 mm in size and females being 10–12 mm in size. In the hackberry emperor females are similarly larger than males. The reason for the sexual dimorphism is due to provision size mass, in which females consume more pollen than males. In some species, there is evidence of male dimorphism, but it appears to be for distinctions of roles. This
16830-564: The female, which looks different from the males. Various other dioecious exceptions, such as Loxostylis alata have visibly different sexes, with the effect of eliciting the most efficient behavior from pollinators, who then use the most efficient strategy in visiting each gender of flower instead of searching, say, for pollen in a nectar-bearing female flower. Some plants, such as some species of Geranium have what amounts to serial sexual dimorphism. The flowers of such species might, for example, present their anthers on opening, then shed
16995-516: The fish (possibly due to overfishing) and otters (cause unknown) have had steep 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
17160-705: The following fish species: rainbow trout ( Oncorhynchus mykiss ), white catfish ( Ameiurus catus ), rock greenling ( Hexagrammos lagocephalus ), Pacific cod ( Gadus macrocephalus ), Atka mackerel ( Pleurogrammus monopterygius ), largemouth bass ( Micropterus salmoides ), northern pike ( Esox lucius ), striped bass ( Morone saxatilis ), dogfish shark ( Squalidae.sp ) and Blue walleye ( Sander vitreus ). Fish taken by bald eagles varies in size, but bald eagles take larger fish than other piscivorous birds in North America, typically range from 20 to 75 cm (7.9 to 29.5 in) and prefer 36 cm (14 in) fish. When experimenters offered fish of different sizes in
17325-544: 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 . In March 2024, bald eagles were found nesting in Toronto for the first time. The birds primarily gather along the Squamish and Cheakamus Rivers, attracted by
17490-651: The form of reduced survival. This means that even if the trait causes males to die earlier, the trait is still beneficial so long as males with the trait produce more offspring than males lacking the trait. This balance keeps dimorphism alive in these species and ensures that the next generation of successful males will also display these traits that are attractive to females. Such differences in form and reproductive roles often cause differences in behavior. As previously stated, males and females often have different roles in reproduction. The courtship and mating behavior of males and females are regulated largely by hormones throughout
17655-734: The fossil record. Stegosaurians A 2015 study on specimens of Hesperosaurus mjosi found evidence of sexual dimorphism in the shape of the dermal plates. Two plate morphs were described: one was short, wide, and oval-shaped, the other taller and narrower. In a large proportion of mammal species, males are larger than females. Both genes and hormones affect the formation of many animal brains before " birth " (or hatching ), and also behaviour of adult individuals. Hormones significantly affect human brain formation, and also brain development at puberty. A 2004 review in Nature Reviews Neuroscience observed that "because it
17820-430: 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
17985-702: 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
18150-723: 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. Bald eagles are able to swim, in some cases dragging its catch ashore with its talons, 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
18315-705: The head or thorax expressed only in the males. Copris ochus also has distinct sexual and male dimorphism in head horns. Another beetle with a distinct horn-related sexual dimorphism is Allomyrina dichotoma, also known as the Japanese rhinoceros beetle . These structures are impressive because of the exaggerated sizes. There is a direct correlation between male horn lengths and body size and higher access to mates and fitness. In other beetle species, both males and females may have ornamentation such as horns. Generally, insect sexual size dimorphism (SSD) within species increases with body size. Sexual dimorphism within insects
18480-400: The highest density of photoreceptors, and provide the highest points of visual acuity. The deep fovea points forward at an approximate 45° angle, while the shallow fovea points approximately 15° to the right or left of the head axis. Several raptor species repeatedly cock their heads into three distinct positions while observing an object. First, is straight ahead with their head pointed towards
18645-769: The highly acute deep fovea. Like all birds, raptors possess tetrachromacy , however, due to their emphasis on visual acuity, many diurnal birds of prey have little ability to see ultraviolet light as this produces chromatic aberration which decreases the clarity of vision. Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different morphological characteristics, including characteristics not directly involved in reproduction . The condition occurs in most dioecious species, which consist of most animals and some plants. Differences may include secondary sex characteristics , size, weight, color, markings, or behavioral or cognitive traits. Male-male reproductive competition has evolved
18810-556: 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
18975-444: The larger males are better at coping with the difficulties of migration and thus are more successful in reproducing when reaching the breeding destination. When viewing this from an evolutionary standpoint, many theories and explanations come into consideration. If these are the result for every migration and breeding season, the expected results should be a shift towards a larger male population through sexual selection. Sexual selection
19140-888: The largest subspecies ( Branta canadensis maxima ) has been reported. Other large waterbird prey include common loons ( Gavia immer ) of all ages. Large wading birds can also fall prey to bald eagles. For the great blue herons ( Ardea herodias ), bald eagles are their only serious enemies of all ages. Slightly larger Sandhill cranes ( Grus canadensis ) can be taken as well. While adult whooping cranes ( Grus americana ) are too large and formidable, their chicks can fall prey to bald eagles. They even occasionally prey on adult tundra swans ( Cygnus columbianus ). Young trumpeter swans ( Cygnus buccinator ) are also taken, and an unsuccessful attack on an adult swan has been photographed. Bald eagles have been occasionally recorded as killing other raptors . In some cases, these may be attacks of competition or kleptoparasitism on rival species but end with
19305-594: 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
19470-508: The male's ability to collect large shells depends on his size. The larger the male, the larger the shells he is able to collect. This then allows for females to be larger in his brooding nest which makes the difference between the sizes of the sexes less substantial. Male–male competition in this fish species also selects for large size in males. There is aggressive competition by males over territory and access to larger shells. Large males win fights and steal shells from competitors. Another example
19635-721: 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
19800-605: 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. Bird of prey Birds of prey or predatory birds , also known as raptors , are hypercarnivorous bird species that actively hunt and feed on other vertebrates (mainly mammals , reptiles and other smaller birds). In addition to speed and strength, these predators have keen eyesight for detecting prey from
19965-513: 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
20130-593: The more ornamented or brightly colored sex. Such differences have been attributed to the unequal reproductive contributions of the sexes. This difference produces a stronger female choice since they have more risk in producing offspring. In some species, the male's contribution to reproduction ends at copulation, while in other species the male becomes the main (or only) caregiver. Plumage polymorphisms have evolved to reflect these differences and other measures of reproductive fitness, such as body condition or survival. The male phenotype sends signals to females who then choose
20295-692: The most common causes for mortality in young fish. Most flowering plants are hermaphroditic but approximately 6% of species have separate males and females ( dioecy ). Sexual dimorphism is common in dioecious plants and dioicous species. Males and females in insect-pollinated species generally look similar to one another because plants provide rewards (e.g. nectar ) that encourage pollinators to visit another similar flower , completing pollination . Catasetum orchids are one interesting exception to this rule. Male Catasetum orchids violently attach pollinia to euglossine bee pollinators. The bees will then avoid other male flowers but may visit
20460-603: The most important variables in shaping distribution areas, and also the geographic dissimilarities may mask important relationships between life history traits and migratory behaviours. The West Palearctic-Afrotropical and the North-South American migratory systems are fundamentally different from the East Palearctic-Indomalayan system, owing to the presence versus absence of ecological barriers." Maximum entropy modelling can help in answering
20625-554: 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
20790-821: The narrower definition followed in this page, excluding many piscivorous predators such as storks , cranes , herons , gulls , skuas , penguins , and kingfishers , as well as many primarily insectivorous birds such as passerines (e.g. shrikes ), nightjars , frogmouths , songbirds such as crows and ravens , alongside opportunistic predators from predominantly frugivorous or herbivorous ratites such as cassowaries and rheas . Some extinct predatory telluravian birds had talons similar to those of modern birds of prey, including mousebird relatives ( Sandcoleidae ), and Messelasturidae indicating possible common descent . Some Enantiornithes also had such talons, indicating possible convergent evolution , as enanthiornithines weren't even modern birds . The term raptor
20955-444: The nest and hunting. Larger females are favored because they can incubate larger numbers of offspring, while also being able to brood a larger clutch size. It is a long-standing belief that birds lack any sense of smell, but it has become clear that many birds do have functional olfactory systems . Despite this, most raptors are still considered to primarily rely on vision, with raptor vision being extensively studied. A 2020 review of
21120-596: The nesting trees used by eagles, followed by hemlocks ( Tsuga ) at 20%. Increasingly, eagles nest in human-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
21285-560: The non-breeding seasons. They can take fish up to at least twice their own weight, such as large mature salmons , carps , or even muskellunge ( Esox masquinongy ), by dragging its catch with talons and pull toward ashore. 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
21450-629: The object. Second and third are sideways to the right or left of the object, with their head axis positioned approximately 40° adjacent to the object. This movement is believed to be associated with lining up the incoming image to fall on the deep fovea. Raptors will choose which head position to use depending on the distance to the object. At distances as close as 8m, they used primarily binocular vision. At distances greater than 21m, they spent more time using monocular vision. At distances greater than 40m, they spent 80% or more time using their monocular vision. This suggests that raptors tilt their head to rely on
21615-470: The oldest dates published so far in the case of birds of prey. For example, a previous reconstruction of migratory behaviour in one Buteo clade with a result of the origin of migration around 5 million years ago was also supported by that study. Migratory species of raptors may have had a southern origin because it seems that all of the major lineages within Accipitridae had an origin in one of
21780-424: 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
21945-412: The order Ciconiiformes . The secretary bird and/or osprey are sometimes listed as subfamilies of Acciptridae: Sagittariinae and Pandioninae, respectively. Australia's letter-winged kite is a member of the family Accipitridae , although it is a nocturnal bird. The nocturnal birds of prey—the owls —are classified separately as members of two extant families of the order Strigiformes : Below
22110-503: The order Gruiformes . And they are still not considered birds of prey in general parlance. Their bodies are also shaped completely differently from birds of prey. They have long legs and long necks. While secretarybirds also have long legs, they otherwise resemble raptors. Seriemas do not. Their beak is hooked, but too long. Migratory behaviour evolved multiple times within accipitrid raptors. The earliest event occurred nearly 14 to 12 million years ago. This result seems to be one of
22275-446: 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
22440-450: 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
22605-813: The owls remained monogeneric (family Ægolii, genus Strix ), whilst the diurnal raptors were divided into three families: Vulturini, Gypaëti, and Accipitrini. Thus Vieillot's families were similar to the Linnaean genera, with the difference that shrikes were no longer included amongst the birds of prey. In addition to the original Vultur and Falco (now reduced in scope), Vieillot adopted four genera from Savigny: Phene , Haliæetus , Pandion , and Elanus . He also introduced five new genera of vultures ( Gypagus , Catharista , Daptrius , Ibycter , Polyborus ) and eleven new genera of accipitrines ( Aquila , Circaëtus , Circus , Buteo , Milvus , Ictinia , Physeta , Harpia , Spizaëtus , Asturina , Sparvius ). Falconimorphae
22770-833: The placement of the birds of prey. Their analysis has found support in a clade consisting of the Strigiformes and Accipitriformes in new clade Hieraves . Hieraves was also recovered to be the sister clade to Australaves (which it includes the Cariamiformes and Falconiformes along with Psittacopasserae ). Below is their phylogeny from the study. Coraciimorphae (woodpeckers, rollers, hornbills, etc.) [REDACTED] Strigiformes (owls) [REDACTED] Accipitriformes (hawks, vultures, and relatives) [REDACTED] Cariamiformes (seriemas) [REDACTED] Falconiformes (falcons) [REDACTED] Psittacopasserae (parrots and songbirds) [REDACTED] Cariamiformes
22935-436: The plants become sexually mature. Every sexually reproducing extant species of the vascular plant has an alternation of generations; the plants we see about us generally are diploid sporophytes , but their offspring are not the seeds that people commonly recognize as the new generation. The seed actually is the offspring of the haploid generation of microgametophytes ( pollen ) and megagametophytes (the embryo sacs in
23100-668: The predation events are sporadic. In one instance, two bald Eagles fed upon a red fox ( Vulpes vulpes ) that had tried to cross a frozen Delaware Lake . Other medium-sized carnivorans such as striped skunks ( Mephitis mephitis ), American hog-nosed skunks ( Conepatus leuconotus ), and common raccoons ( Procyon lotor ) are taken, as well as domestic cats ( Felis catus ) and dogs ( canis familiaris ). Other wild mammalian prey include fawns of deer such as white-tailed deer ( Odocoileus virginianus ) and Sitka deer ( Odocoileus hemionus sitkensis ), which weigh around 3 kg (6.6 lb) can be taken alive by bald eagles. In one instance,
23265-418: The presence of specific sex-related behaviour is common to many lizards; and vocal qualities which are frequently observed in frogs . Anole lizards show prominent size dimorphism with males typically being significantly larger than females. For instance, the average male Anolis sagrei was 53.4 mm vs. 40 mm in females. Different sizes of the heads in anoles have been explained by differences in
23430-522: 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
23595-410: The principle. There are two types of dichromatism for frog species: ontogenetic and dynamic. Ontogenetic frogs are more common and have permanent color changes in males or females. Ranoidea lesueuri is an example of a dynamic frog with temporary color changes in males during the breeding season. Hyperolius ocellatus is an ontogenetic frog with dramatic differences in both color and pattern between
23760-408: The production of more exaggerated ornaments in males may come at the cost of suppressed immune function. So long as the reproductive benefits of the trait due to sexual selection are greater than the costs imposed by natural selection, then the trait will propagate throughout the population. Reproductive benefits arise in the form of a larger number of offspring, while natural selection imposes costs in
23925-464: The question: why species winters at one location while the others are elsewhere. Temperature and precipitation related factors differ in the limitation of species distributions. "This suggests that the migratory behaviours differ among the three main migratory routes for these species" which may have important conservational consequences in the protection of migratory raptors. Birds of prey (raptors) are known to display patterns of sexual dimorphism . It
24090-402: 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
24255-585: The same plumage pattern, though the female is clearly distinguishable by reason of her paler or washed-out colour". Examples include Cape sparrow ( Passer melanurus ), rufous sparrow (subspecies P. motinensis motinensis ), and saxaul sparrow ( P. ammodendri ). Examining fossils of non-avian dinosaurs in search of sexually dimorphic characteristics requires the supply of complete and articulated skeletal and tissue remains. As terrestrial organisms, dinosaur carcasses are subject to ecological and geographical influence that inevitably constitutes
24420-479: The sexes, and allometry, but their relative importance is still not fully understood . Sexual dimorphism in birds can be manifested in size or plumage differences between the sexes. Sexual size dimorphism varies among taxa, with males typically being larger, though this is not always the case, e.g. birds of prey , hummingbirds , and some species of flightless birds. Plumage dimorphism, in the form of ornamentation or coloration, also varies, though males are typically
24585-526: The sexes. At sexual maturity, the males display a bright green with white dorsolateral lines. In contrast, the females are rusty red to silver with small spots. The bright coloration in the male population attracts females and is an aposematic sign to potential predators. Females often show a preference for exaggerated male secondary sexual characteristics in mate selection. The sexy son hypothesis explains that females prefer more elaborate males and select against males that are dull in color, independent of
24750-511: The sexual preference in colorful females due to higher egg quality. In amphibians and reptiles, the degree of sexual dimorphism varies widely among taxonomic groups . The sexual dimorphism in amphibians and reptiles may be reflected in any of the following: anatomy; relative length of tail; relative size of head; overall size as in many species of vipers and lizards ; coloration as in many amphibians , snakes , and lizards, as well as in some turtles ; an ornament as in many newts and lizards;
24915-414: The size dimorphic wolf spider Tigrosa helluo , food-limited females cannibalize more frequently. Therefore, there is a high risk of low fitness for males due to pre-copulatory cannibalism, which led to male selection of larger females for two reasons: higher fecundity and lower rates of cannibalism. In addition, female fecundity is positively correlated with female body size and large female body size
25080-408: 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. 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
25245-446: 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
25410-567: The species' vision. Similar sexual dimorphism and mating choice are also observed in many fish species. For example, male guppies have colorful spots and ornamentations, while females are generally grey. Female guppies prefer brightly colored males to duller males. In redlip blennies , only the male fish develops an organ at the anal-urogenital region that produces antimicrobial substances. During parental care, males rub their anal-urogenital regions over their nests' internal surfaces, thereby protecting their eggs from microbial infections, one of
25575-439: 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: The bald eagle forms
25740-471: 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
25905-542: The thousands of free-floating flowers released by a male. Sexual dimorphism is most often associated with wind-pollination in plants due to selection for efficient pollen dispersal in males vs pollen capture in females, e.g. Leucadendron rubrum . Sexual dimorphism in plants can also be dependent on reproductive development. This can be seen in Cannabis sativa , a type of hemp, which have higher photosynthesis rates in males while growing but higher rates in females once
26070-407: 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
26235-460: The whinchat in Switzerland breed in intensely managed grasslands. Earlier harvesting of the grasses during the breeding season lead to more female deaths. Populations of many birds are often male-skewed and when sexual differences in behavior increase this ratio, populations decline at a more rapid rate. Also not all male dimorphic traits are due to hormones like testosterone, instead they are
26400-524: 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. Bald eagles have high mate fidelity and generally mate for life . However, if one pair member dies or disappears, the survivor will choose a new mate. A pair that has repeatedly failed in breeding attempts may split and look for new mates. Bald eagle courtship involves elaborate, spectacular calls and flight displays by
26565-406: 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
26730-540: Was captured near Castleisland , County Kerry on November 15, 1987. There is also a record of it from Llyn Coron, Anglesey, in the United Kingdom, from October 17, 1978; the provenance of this individual eagle has remained in dispute. 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
26895-649: Was dominant prey in San Miguel Island . Due to easy accessibility and lack of formidable nest defense against eagles by such species, bald eagles are capable of preying on such seabirds at all ages, from eggs to mature adults, and they can effectively cull large portions of a colony. 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
27060-470: Was exhibited in the crest of 3 species of hadrosaurids. The crests could be categorized as full (male) or narrow (female) and may have given some advantage in intrasexual mating-competition. Ceratopsians According to Scott D. Sampson, if ceratopsids were to exhibit sexual dimorphism, modern ecological analogues suggest it would be found in display structures, such as horns and frills. No convincing evidence for sexual dimorphism in body size or mating signals
27225-540: 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
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