Accipitridae

(vertebrate zoology) The diurnal birds of prey, the largest and most diverse family of the order Falconiformes, including hawks, eagles, and kites.

(Accipitridae)

Class: Aves

Order: Falconiformes

Suborder: Accipitres

Family: Accipitridae

Thumbnail description
Powerful predators with broad wings, hooked beaks, strong legs and feet, sharp talons, and keen sight; carnivorous hunters and scavengers

Size
7.9–59 in (20–150 cm); 2.6–441 oz (75–12,500 g)

Number of genera, species
64 genera, 236 species, and 535 taxa (species or subspecies)

Habitat
Most habitats from seacoasts to mountains, deserts to wetlands, woodlands and lush forests, remote wilderness and isolated islands to farmlands, suburbs, and cities

Conservation status
Critical: 8, Endangered: 4, Vulnerable: 22, Not Threatened: 24, Data Deficient: 1

Distribution
Worldwide, except the Antarctic and extreme northern Arctic

Evolution and systematics

There are two diurnal raptor families, Accipitridae (hawks, eagles, and allies) and Falconidae (falcons, caracaras, and allies), which have no obvious relatives among the other birds; it is not even agreed that they are closely related to each other. Their similarities, which include strong, sharp beaks, feet, and talons, and forward-directed eyes for stereoscopic vision, may well be evolutionary convergent adaptations to similar lifestyles rather than indicative of taxonomic affinity. This is almost certainly so for the New World vultures, which are now thought to be allied with the storks.

The accipitrid family can be split into two subfamilies. The subfamily Pandioninae has only one representative, the osprey, whose relationship to the other hawks and eagles remains controversial. Hence it is sometimes placed in its own monospecific family. Its fossil record extends back at least to the Miocene—10–15 million years ago (mya). By the late Miocene, the osprey was already widespread with virtually the same form and distribution as today.

Fossil representatives of the other subfamily, the Accipitrinae (the hawks, eagles, and allies), have been found in Tertiary deposits (30–50 mya). These were buzzard-like raptors that bear no obvious relationship to any living raptor. They first appeared in South America and were widespread by the Miocene. Also widely distributed at this time were the Old World vultures, which no longer occur in the Americas, a clear indication that present day distributions do not necessarily reflect evolutionary origins. By the end of the Miocene (5 mya), when the fossil record improves, many of the modern raptor forms had already appeared.

The number of species and subspecies in taxonomic lists of the family varies depending on the views of the author, and molecular studies have been of limited use in clarifying relationships. Some genera such as Morphnus have only one representative (monotypic). At the other extreme, the genus Accipiter contains about 50 species (polytypic). Some species have been split into a multitude of subspecies—the aptly named variable goshawk (Accipiter novaehollandiae) has about 23—others are monotypic. A good many of these arrangements do not stand close scrutiny, particularly for little known taxa.

For convenience, the accipitrids are often split into groups of like species. These "natural" groups attempt to reflect general evolutionary trends within the family, from the so-called "primitive," less predatory species to the more "advanced," highly predatory forms:

1. The kites lack the bony eye shield ("brow") which gives many of the other accipitrids a fierce expression. The (a) white-tailed kites (Elanus, Chelictinia, Gampsonyx) have ungrooved talons, unlike the other accipitrids, and eat mammals and insects. Arguably, the most primitive group of kites are (b) unusual specialist feeders (Aviceda, Macheiramphus, Pernis, Leptodon, Chondrohierax) that eat caterpillars and mantids (Aviceda), bats (Macheiramphus), wasp nests (Pernis, Leptodon), and arboreal snails (Chondrohierax). On the one hand, they link to the (c) Australasian endemic kites, which include Lophoictinia, Hamirostra, and Henicopernis, and, on the other, to (d) the South American forms Rostrhamus, Ictinia, and Harpagus. In turn these (c and d) are linked to the next group of kites, (e) the typical kites Milvus and Haliastur, by the fact that that they all have the basal joint of the middle toe fused with the next joint. The (f) fish-eagles (Haliaeetus, Ichthyophaga) are basically large typical kites represented by 10 species which replace each other geographically. Several other, large, powerful Australasian/South American species (g) including Erythrotriorchis, Megatriorchis, Harpia, Harpyopsis, and Pithecophaga may also be offshoots or relict forms of the kite radiation.
2. Old World vultures, 15 species, all scavengers. For example, Gypaetus, Gyps, and Torgus, whose closest relatives are probably the fish-eagles.
3. Serpent-eagles, made up of 15 species of snake eaters, such as Circaetus, Terathopius, and Spilornis, possibly also have close links with the kites.
4. Harriers (Circus) and harrier-hawks (Polyboroides), the latter most closely related to the serpent-eagles.
5. Goshawks, containing about 58 species of "true" hawks, including chanting goshawks (Melierax), goshawks, and sparrowhawks (Accipiter).
6. Buzzard-like hawks, a grab-bag of species that may not all belong together, including Parabuteo, Buteogallus, Butastur, and Geranoaetus.
7. Typical buzzards (Buteo) with 28 species.
8. Typical eagles containing 33 species, including Aquila, Hieraaetus, and Spizaetus, which, like Buteo, have feathered legs.

Physical characteristics

The familiar characteristics of the birds of prey include the strongly hooked beak and, at is base, the bare, often brightly colored cere in which the nostrils are situated. Features that distinguish the hawks and eagles (accipitrids) from the other raptorial family, the falcons and caracaras, include several skeletal differences, yellow, red, or hazel eyes (vs. brown), well-developed nest-building behavior (vs. absent or poor), and the forceful squirting of excreta (vs. dropping of excreta).

Members of the family range in size from tiny active hunters, the South American pearl kite (Gampsonyx swainsonii) and African little sparrowhawk (Accipiter minullus), both weighing less than 3.5 oz (100 g) and with wingspans of 21 and 39 in (54 and 39 cm), respectively, to the Himalayan vulture (Gyps himalayensis), a hulking scavenger with a wingspan exceeding 9 ft (3 m) and weight reaching to 26 lb (12.5 kg), and the fearsome harpy eagle (Harpia harpyja) and Steller's sea-eagle (Haliaeetus pelagicus), both reaching 20 lb (9 kg) and the largest of all flying predators.

The hawks and eagles occur in a great variety of forms. The basic types are kites and vultures, hawks and eagles, and within each there are weaker and stronger forms, and mildly predatory and highly predatory species. For example, all the vultures are scavengers but some have immensely robust beaks to tear tough skin and tendons, whereas others have long, lightweight beaks to reach deep into the carcass to nibble tender parts and still others rely on scraps left by large vultures and other predators. The vultures have rather weak feet and stubby, flattish talons that are not used to clutch prey, compared with the eagles with their powerful grasp and dagger-like talons that hold and squeeze the prey. The more powerful eagles that hunt large, difficult prey have deep powerful bills and stout legs, whereas those that eat smaller, more easily captured prey have quite gracile bills and slender legs. The long, double-jointed legs of the harrier-hawks (Polyboroides) allow them to reach deep in to tree holes to extract nestling birds.

Form also reflects function in wings and tail shapes. Short-winged, long-tailed hawks are adept at flight through the confines of forest; long, broad-winged, broad-tailed forms are soarers that ride wind currents to great height and cover vast distances effortlessly. Both the African bateleur (Terathopius ecaudatus) and Australian black-breasted buzzard (Hamirostra melanosternon) have long, broad wings and very little tail, characteristics of hawks that glide low for long distances and have little need of agility. Migrants are longer-winged than nonmigrants, particularly those that use active flight to travel across the world. Even within a species, such as the osprey, migratory populations are longer-winged than those that are sedentary.

Vultures and other scavenging raptors that delve into carcasses have parts of their face, head, and even neck bare of feathers, presumably for cleanliness. Most species are rather cryptic shades of gray, brown, or whitish, often streaked or barred ventrally, depending upon their typical habitat. A few hawks have plumage morphs such that two or more color forms occur and interbreed.

In most species the sexes share similar plumage, although the male may be slightly brighter; exceptions include several harriers in which the female is brown and the male gray (dichromatism). Immatures tend to be more brown or heavily marked than adults or, in species with sexual dichromatism, most like the adult female. An interesting feature of the family is that females are larger than males (dimorphism). This is most obviously so in the species that kill relatively large prey that is difficult to catch. Hence the vultures are only slightly dimorphic, whereas in many of the sparrowhawks the female is twice as heavy as the male.

All raptors have keen eyesight, with particular sensitivity to movement. To help them distinguish their green insect prey from green vegetation, the eyes of bazas (Aviceda) have red oil droplets that act like filters. Bazas and other similar kites, which are relatively non-predatory, have quite laterally placed eyes, whereas active pursuers such as accipiters have more forward placed eyes for greater stereoscopic vision. Crepuscular hunters and the few species that are truly nocturnal, such as the letter-winged kite (Elanus scriptus), also depend on sight and have relatively large eyes and hunt by moonlight. A few species, including the bat hawk and harriers, are quite reliant on hearing to help them locate concealed prey and have a facial disc of stiff feathers that funnels sounds to their large ear openings. The sense of smell does not seem to be particularly important. Unlike some of the New World vultures, the accipitrid vultures do not have well-developed sense of smell to lead them to carrion.

Distribution

The family has an almost world-wide distribution although only one species occurs in the high Arctic and none in the Antarctic. Some genera, such as Accipiter, are extremely widespread, occurring on many islands and all continents except Antarctica. Others have a much more restricted distribution; for example, the great Philippine eagle (Pithecophaga jefferyi) is found only on large islands of the Philippines.

Many species with Arctic breeding grounds vacate them after breeding for more benign climates, sometimes flying across the globe, from North to South America or Europe to Africa. Where the climate is stable or moderate all year species tend to be resident. Elsewhere, they may escape the harshest season: in some species the population simply shifts its range slightly southwards, other species stay put in some regions and all or part of the population migrates from other regions.

Only one species has been successfully introduced to a part of the world where it was not endemic. The Pacific marsh harrier (Circus approximans) was taken to Tahiti in about 1885 to control rodents, and self-spread to other islands in the Society Group. Races of several other species have been translocated as part of reintroduction programs for conservation purposes.

Habitat

The hawks, eagles, and their allies are found in most habitats throughout the world. Forests and woodlands support the most species, especially in tropical areas. Poorer, less varied habitats such as tundra, desert steppe, and intensive agriculture support few species. Small or isolated oceanic islands may have one or no species. Even the large islands of New Zealand have only one species, the Pacific marsh harrier.

Many raptors prefer particular habitats, for example, the goshawks and sparrowhawks, genus Accipiter, favor forest and woodland, and the harriers (Circus) require flat, treeless areas. Other species, such as Swainson's hawk (Buteo swainsoni), are more generalized, ranging over many habitats.

Sea coasts from Asia to the arctic support sea-eagles, and they are joined by ospreys (Pandion haliaetus) and Brahminy kites (Haliastur indus) on warmer Asian-Australasian coasts, and also frequent large inland waterbodies. Several species frequent ecotones, where two or more habitats meet. The Australian black-breasted buzzard may nest and roost along broad, dry inland watercourse but hunts far out into the surrounding desert and savanna. Sea-eagles require trees or cliffs for nesting but hunt along shoreline and in-shore waters. Some species, such as the kites (Elanus) and harriers, can hunt where groundcover is long, others need lower groundcover to hunt successfully. Indeed structure seems to be more important than vegetation composition.

Migrants tend to occupy similar habitats at either end of their migration path. The pallid harrier (C. macrourus) moves from breeding grounds in the grassy plains and dry steppes of middle Europe to similar "wintering" habitats in Africa and India. Its congener, the western marsh harrier (C. aeruginosus), makes the same trip, but favors reedy wetlands.

Towns and cities with parks, open spaces, and abundant prey can support a number of species including sparrowhawks. Where sanitation is poor and rubbish dumps common a number of species live communally with humans. For example, black kites (Milvus migrans), hooded vulture (Necrosyrtes monachus), and Indian white-backed vulture (Gyps bengalensis) thrive around settlements and cities in parts of Africa and India.

Behavior

Most hawks and eagles are active by day, usually during the period when their prey is most mobile. Some of the largest species are dependent on the heat of the day to create thermals to help them get them airborne and carry them high and far. When resting they perch quietly, often in a sheltered position on a cliff or among foliage. At the perch, they spend considerable time in feather maintenance, keeping their plumage clean, parasite free, and well aligned. Most species have an oil gland at the base of the tail from which they spread oil through the feathers, although a few, such as the Elanus kites, have powder down (special feathers that flake into a fine powder that is spread through the plumage to clean it). Many species bathe, sometimes by flying through wet foliage but mostly by wading into water.

The majority of hawks and eagles are solitary but several are colonial and hunt, roost, and breed in numbers. Even some solitary species, such as the steppe eagle (Aquila nipalensis), become more gregarious outside the breeding season and forage and roost with other individuals or species where food is plentiful.

Even though they are capable predators, aggressive encounters between individuals seldom progress beyond displays and bluffing. The naked skin on the head of the lappet faced vulture (Torgos tracheliotus) "blushes" with emotion. Several species, for example, the long-crested eagle (Lophaetus occipitalis) and booted eagle (Hieraaetus pennatus), have crests which they raise when threatened.

Hawks and eagles make greatest use of their voices during the breeding season, to defend and advertise territories and in courtship and breeding. For any particular species the range of calls used is usually very limited: often simply repeated whistles, mews, barks, cackles, yelps, or chitters. A few species have far-carrying melodic calls. The whistling kite (Haliastur sphenurus) throws its head back to make a single leisurely, descending whistle followed by a staccato series rising in pitch. In contrast, its larger cousin the white-bellied sea-eagle (Haliaeetus leucogaster), which also throws its head back, emits a series of goose-like honks that echo across the landscape. The vultures hiss and spit when squabbling but are otherwise silent. In fact, outside the breeding season, most hawks and eagles are seldom vocal.

Especially in the northern hemisphere, species or populations in cooler areas often vacate their breeding grounds to travel to milder climates, where food is more plentiful, in the non-breeding season. Broad-winged species, such as the broad-winged hawk (Buteo platypterus), use thermals and updraughts to fly long distances with few stops. Other species, including Eurasian sparrowhawks (Accipiter nisus) and pallid harrier (C. macrourus), are more active fliers and frequently stop to feed in suitable habitat between breeding and wintering grounds. Where migration routes are channeled at narrow sea crossings, land bridges, or between mountains, migrating raptors may fill the sky. The autumn movement of raptors of several species between North and South America concentrates spectacularly at the isthmus of Panama; 2.6 million have been counted passing through.

Feeding ecology and diet

All the hawks and eagles are carnivorous and most eat only freshly caught prey. Some eat carrion at times or almost exclusively, although rarely truly putrid flesh, and a few eat vegetable and other organic matter.

Crabs gathered from coastal mangroves are almost the exclusive diet of the crab hawk (Buteogallus aequinoctialis), whereas the white-necked hawk (Leucopternis lacernulata) appears to specialize on insects, especially those flushed by ants, monkeys, birds, and humans, and only takes a few vertebrates. The bat hawk (Macheiramphus alcinus) has a wide gape to swallow bats whole. Wasps and hornets, larvae, pupae, and adults, plucked from the comb, are the favored food of the honey-buzzards (Pernis apivorus). Palm nuts are the main food of the palm nut vulture (Gypohierax angolensis), although it does eat some invertebrates, fish, crabs, and carrion, and the bearded vulture (Gypaetus barbatus) lives on bones left by other scavengers. The osprey (Pandion haliaetus) rarely eats anything but fish. The dynamics of Elanus kite populations are closely tied to cyclic populations of the rodents on which they are dependent. At the other extreme, the generalist feeder, the red kite (Milvus milvus) hunts small animals and eats almost anything organic, alive or dead.

Some of the larger eagles are among the most potent of predators, regularly overpowering prey as large or larger than themselves. The most powerful hunt big, dangerous prey: the South American harpy eagle (Harpia haryja) takes adult monkeys, sloths, porcupines, and the largest of the massive-billed parrots; in Africa, the crowned eagle (Stephanoaetus coronatus) weighs 6–8 lb (3–4 kg) but hunts monkeys, small antelope, and other animals up to 40 lb (20 kg) and the 2–3 lb (1–1.5 kg) ornate hawk-eagle (Spizaetus ornatus) hunts toucans, macaws, squirrels, and agoutis. The 6–8 lb (3–4 kg) Australian wedge-tailed eagle (Aquila audax) eats a range of prey, including medium-sized birds, mammals, reptiles, and carrion, and occasionally hunts cooperatively to exhaust and kill adult kangaroos and dingoes many times its own weight. In contrast, the very similar Verreaux's eagle (Aquila verreauxii) of Africa specializes on hyrax, which it takes by surprise from rock outcrops. Several of the accipiters (goshawks and sparrowhawks) are among the swiftest and most agile of aerial hunters, overtaking birds after a brief pursuit through forest or woodland.

Within species, prey captured varies seasonally, young individuals take easier prey (especially abundant invertebrates) and, during the breeding season, adults tend to take more vertebrates than in other seasons.

Searching and hunting methods vary according to the main prey types and habitats. Vultures and some larger open country eagles soar to great height and search over great distances. The bateleur spends long hours on the wing effortlessly gliding low (about 16 ft [50 m] above ground) to search for, surprise and flush prey from the ground. The harriers quarter open country, flapping slow and low, up and down a field or wetland. Still other species sit and wait at a perch and make short sallies out to pursue passing prey. The Elanus kites hover into the slightest breeze and drop onto small mammals below. Especially in the non-breeding season, many species gather opportunistically at termite agates and rodent and locust plagues. Species with the most generalized of diets usually use the most diverse range of hunting techniques. The sea-eagles wade into water after fish, swoop from the air to scoop it from the water, pursue rabbits across the land, scavenge along the shoreline, and frequently harry other predators for their kill.

Some species use assisted hunting, either with their own kind or with other animals, machinery, or fire. Pairs of the great Philippine eagle (P. jefferyi) hunt cooperatively: one bird distracts the monkey troop while the other strikes. The plumbeous kite (Ictinia plumbea) feeds in association with marmosets as they move through the forest, catching the cicadas they flush. Attracted for miles by the smoke, roadside hawks (Buteo magnirostris) gather at fires to catch animals fleeing the flames.

Small hawks and eagles must feed more often than large ones, and species that eat easily captured prey may have to spend more time gathering or locating prey than those that eat large, difficult prey. Sparrowhawks hunt at least daily, eagles typically hunt every few days, and a large vulture may need to gorge only once a fortnight or so.

Hunters of live prey mostly capture and kill with their feet, and the bill is used in opposition to the feet to dissect prey. The snail eaters have their own characteristic techniques: the hook-billed kite (Chondrohierax unicinctus) uses its robust upper mandible to forcefully break open the whorls of the shell, whereas, with their long modified bills, the snail kites (Rostrhamus) sever the columellar muscle that attaches the snail to the shell.

Reproductive biology

Most raptors defend a breeding territory from conspecifics and other intruders. This may be the area immediately around the nest or a wider area. Spacing between nests tends to be quite regular, where nest sites allow. Pairs of colonial species, such as Rüppell's vulture (Gyps rueppellii) and letter-winged kite, nest on the same cliff or share a tree with other pairs. The larger predatory species space more widely, tens of kilometers apart, closer where food is most available. Territorial activity is usually most vigorous as the breeding season approaches, when boundaries are advertised in some species by spectacular display flights.

Most species are monogamous and only a handful vary from this. Polygamy is known to be common only in three harrier species, including Montagu's harrier (Circus pygargus), for which breeding resources (food and nest sites) are concentrated. Experienced males are able to defend and support two or more females, although the primary female and her brood get the larger share of food captured by the male. In parts of their range where food is less available, Harris' hawks (Parabuteo unicinctus) breed in cooperative groups, where the core pair are assisted by unrelated helpers and young from the previous breeding attempt.

Typically, in the more predatory species the male feeds the female as part of courtship and continues to supply food during incubation and when the chicks are small; once the nestlings can maintain their own body heat, the female also hunts. In all but the vultures, which share nest duties, the female tears up the food and distributes it among the young.

All accipitrids build a nest of sticks lined with softer material. Nest sites are usually in a commanding position on a cliff or in a tree, but a few species such as the harriers nest on the ground. In some species successive generations return to reuse a traditional site for decades.

Most species breed annually, in the season when food is predictable and abundant, usually spring. The largest eagles attempt to breed every second year. Species that depend on prey that has extremes of population size, such as the plaguing rodents, tend to breed when the opportunity arises, regardless of season, and continue to breed until prey numbers subside.

The eggs are oval, mainly white marked with shades of brown, red, and purplish gray. Larger species tend to lay one or two eggs and smaller species three or more; and clutch sizes tend to be larger in harsher climates. Rodent specialists, such as the rough-legged buzzard (Buteo lagopus), show the greatest extremes; they lay very large clutches in years of plenty and have small clutches or do not breed in poor rodent years.

The length of the incubation period ranges from about three-and-a-half weeks in small sparrowhawks to 21 weeks in the harpy eagle. Chicks stay in the nest for a similar period and, once fledged, are dependent for several more weeks as they gradually learn to hunt.

A feature of some species is siblicide, in which the first hatched chick kills its sibling. In a few species, including Verreaux's eagle, this is obligatory and no second chicks survive. In other species it depends on the availability of food and brood size is adjusted to suit the conditions: when food is scarce weak nestlings are killed and eaten so that there is no wastage and the chances of survival of the remaining chick(s) improve.

Conservation status

In the 2000 IUCN world listing 34 species are assessed as Threatened—8 Critically Endangered, 4 Endangered, and 22 Vulnerable. None have become extinct since 1600, but several species were lost from large islands in historical times, following early colonization by humans, among them Haast's eagle (Harpagornis moorei), a huge moa-eating eagle of New Zealand.

Not surprisingly, species with small distributional ranges tend to be most vulnerable and these are often on islands. Among the most endangered species, two are in Cuba, where less than 250 individuals of the Cuban kite (Chondrohierax wilsonii) and about 300 of Gundlach's hawk (A. gundlachii) survive and continue to decline from deforestation and persecution. The Reunion harrier (C. maillardi) is under pressure from increasing urbanization, persecution, and poaching but since protection was tightened in the 1970s, public awareness has increased and numbers have increased to 200–340. On continents, species with very small distributions include the white-collared kite (Leptodon forbesi) of the humid forests of north-east Brazil, where there has been massive logging; this population is thought to number less than 250 individuals. The Spanish imperial eagle (Aquila adalberti), with an estimated total population of 252, is declining from deforestation and persecution, in this case by poisoning at game hunting reserves.

The large island of Madagascar has the greatest number of Threatened species. The Madagascar harrier (Circus macrosceles), serpent-eagle (Eutriorchis astur), and fish-eagle (Haliaeetus vociferoides)—the latter two of which are thought to have populations of less than 250 individuals—are all declining and threatened by habitat loss and degradation. The fish-eagle also suffers from human hunting and persecution. Another two species are Near Threatened: Henst's goshawk (A. henstii) and the Madagascar sparrowhawk (A. madagascariensis) are confronted by problems from widespread deforestation.

More specialized species suffer more particular threats. The huge vultures—white-rumped (Gyps bengalensis), long-billed (G. indicus), Cape griffon (G. coprotheres), and lappet-faced—fall victim to poison left in carcasses for control of other predators and, at the same time, find fewer carcasses and refuse on which to feed, in part because of competition from humans. Human pressure—from such threats as over-fishing, coastal development, and hydroelectric schemes—is a common problem to another three sea-eagles Sanford's, Steller's (H. pelagicus), and Pallas's (H. leucoryphus). Yet, human caused habitat loss to development and natural resource harvesting threatens by far the greatest number of species.

Remedial action has re-established or stabilized some species. The organochlorine pesticides (including DDT, which causes raptors to lay thin-shelled eggs, and dieldrin, which causes direct mortality) caused massive population decreases in species such as the Eurasian sparrowhawk (Accipiter nisus) in the 1960s and 1970s; populations began to recover when until the chemicals were banned in developed countries. Many countries give raptors full legal protection, which has lessened persecution and disturbance. Some populations have been assisted by hands-on conservation efforts. The whitetailed eagle (H. albicilla), which last bred in the British Isles in 1908, has been successfully reintroduced to Scotland. Northern goshawk (A. gentilis) and red kite, absent from Britain for more than a century, have also been re-established, the former aided by escaped falconers birds. By protection, provision of food, and careful attention to their sociable nature, the Eurasian griffon (Gyps fulvus) has been returned to the mountains of south-central France. Nest protection, erection of artificial nest sites, and breeding manipulation by double-clutching and egg and nestling translocation has benefited the recovery of species such as the bald eagle (Haliaeetus leucocephalus) in the United States and the osprey in Britain. A handful of species has adapted to life in cities, croplands, and plantations, but for the majority of accipitridae, particularly those that are large or highly specialized, the long-term prognosis is poor.

Significance to humans

Birds of prey have long been admired for their hunting prowess and powers of flight and sight. Paradoxically, they are also despised for their depredations on livestock and perceived cruelty; their fortunes fluctuating with the times.

In ancient Egypt, the Eurasian griffon was worshipped, appearing in the crown of the goddess of childbirth Nekhebet, and a vulture headdress was the privilege of a queen. On victory steles, vultures carried away bodies of vanquished. In some parts of the world supernatural hawks took on a part-human form or were fearful messengers of more human-like gods. Greek legend has Zeus's eagle stealing the beautiful Ganymede to make him cupbearer to the gods of Olympus. Garuda, the steed of the Hindu god Vishnu, has the red wings and white face of the Brahminy kite; its image guards the sacred temples at Angkor and elsewhere. The thunderbird of many tribes from the Americas to the Cook Islands often took the form of a terrifying, eagle-like bird that brought rain or created the world. From Tibet to the Nile Valley mythical eagles were worshipped as harbingers of the wind, stars, sun, and rain and protectors of the gods and their earthy representatives, including the Inca emperors. In early Christianity the eagle signified escape and fulfillment. Because of such associations, they were often an essential part of the trappings of nobility. The German imperial two-headed eagle of medieval heraldry signified the power of emperors. Even today images of eagles appear on coats of arms and company logos, symbols of strength and reliability.

One of the closest relationships between humans and raptors is falconry or hawking. As early as 2000 B.C. in Asia, humans were hunting with trained hawks. The practice flourished in Europe and the middle East from A.D. 500 to 1600 and was practical, providing fresh meat for the table, as well as recreational. In these feudal societies there was often strict hierarchy: the upper classes were allowed the more prestigious species including the larger falcons and eagles and the middle classes less desirable birds such as Eurasian sparrowhawk and northern goshawk. There are still devotees of the sport, particularly among Arabian royalty, and the custom continues in some central Asian tribes, where golden (Aquila chrysaetos) and imperial eagles (A. heliaca) are used to hunt wolves, foxes, and gazelles from horseback. However, in many developed countries falconry is not allowed, mainly for conservation and ethical (animal rights) reasons. Where it is legal, there are restrictions on the keeping of birds and taking from the wild and many are now bred in captivity.

The modern era brought a lessening of superstitions and with the widespread introduction of firearms hawks were no longer a useful means of hunting. Fear and loathing replaced the general reverence for raptors and they were persecuted in their millions, sometimes fueled by government sponsored bounties. Although a few larger species occasionally prey on young livestock such as cattle, sheep, reindeer, or poultry, their impact on healthy herds is invariably exaggerated. Even harmless species, tarred with the same brush, have suffered. Today, livestock is better managed, and as many raptor populations dwindle there is increasing concern for their conservation and appreciation of their beauty and role in nature. Large-scale egg and specimen collecting, popular for much of the 1900s and which had a local impact on thinly scattered, already beleaguered raptor populations, is no longer fashionable. Nevertheless, many hawks are still are trapped, shot, or poisoned to protect livestock and thousands are destroyed (sometimes for food or medicine) where they gather in numbers on migration through Europe, China, and elsewhere. Body parts of the critically endangered Madagascar fish-eagle (Haliaeetus vociferoides) continue to be used in traditional medicines. Conversely, in the Solomon Islands, breakdown of traditional taboos now allows hunting that threatens Sanford's sea-eagle (H. sanfordi).

Species accounts

Resources

BirdLife International. Threatened Birds of the World. Barcelona and Cambridge: Lynx Edicions and BirdLife International, 2000.

Brown, L. H., E. K. Urban, and K. Newman. The Birds of Africa. Vol. 1. London: Academic Press, 1982.

Coates, B. J. The Birds of New Guinea. Vol. I, Non-Passerines. Dove Publications: Alderley, 1985.

Cramp, S., ed. The Birds of the Western Palearctic. Vol. II, Hawks to Bustards. Oxford: Oxford University Press, 1980. del Hoyo, J. A., A. Elliot, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 2, New World Vultures to Guineafowl. Barcelona: Lynx Edicions, 2000.

Ferguson-Lees, J. Raptors: An Identification Guide to the Birds of Prey of the World. Academic Press: New York, 2001.

Fox, N. Understanding the Bird of Prey. Surrey: Hancock House, 1995.

Long, J. L. Introduced Birds of the World. Sydney: Reed, 1981.

Marchant, S. and P. J. Higgins, eds. Handbook of Australian, New Zealand and Antarctic Birds. Vol. 2, Raptors to Lapwings. Oxford: Melbourne, 1993.

Newton, I., and P. Olsen, eds. Birds of Prey. London: Merehurst, 1990.

Olsen, P. Australian Birds of Prey. University of Sydney and Baltimore: New South Wales Press and Johns Hopkins, 1995.

Poole, A. F. Ospreys: A Natural and Unnatural History. Cambridge University Press: Cambridge, 1989.

The Hawk and Owl Trust. 11 St Marys Close, Newton Abbot, Abbotskerswell, Devon TQ12 5QF United Kingdom. Phone: +44 (0)1626 334864. Fax: +44 (0)1626 334864. E-mail: hawkandowl@aol.com Web site:

Raptor Research Foundation. P.O. Box 1897, 810 E. 10th Street, Lawrence, Kansas 66044-8897 USA. Web site:

World Center for Birds of Prey, The Peregrine Fund. 566 West Flying Hawk Lane, Boise, Idaho 83709 USA. Phone:(208) 362-3716. Fax: (208) 362-2376. E-mail: tpf@peregrinefund.org Web site:

World Working Group on Birds of Prey and Owls. P.O. Box 52, Towcester, NN12 7ZW United Kingdom. Phone: +44 1 604 862 331. Fax: +44 1 604 862 331. E-mail: WWGBP@aol.com Web site:

[Article by: Penny Olsen, PhD]

The noun has one meaning:

Meaning #1: hawks; Old World vultures; kites; harriers; eagles
  Synonym: family Accipitridae

Accipitridae Fossil range: Eocene - Recent
Juvenile Ornate Hawk-eagle Spizaetus ornatus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Accipitriformes (or Falconiformes, q.v.) Family: Accipitridae Vieillot, 1816
Subfamilies
Accipitrinae Aegypiinae Buteoninae Circaetinae Circinae Elaninae Milvinae Perninae but see text

The Accipitridae is one of the two major families within the order Accipitriformes (the diurnal birds of prey). Many well-known birds, such as hawks, eagles, kites, harriers and Old World vultures are included in this group. The Osprey is usually placed in a separate family (Pandionidae), as is the Secretary bird (Sagittariidae), and the New World vultures are also usually now regarded as a separate family or order. Karyotype data^[1] indicated that the accipitrids hitherto analysed are indeed a distinct monophyletic group, but whether this group should be considered a family of the Falconiformes or one or several order(s) on their own is a matter of taste.

The accipitrids are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a few feeding on fruit. The Accipitridae have a cosmopolitan distribution, being found on all the world's continents (except Antarctica) and a number of oceanic island groups. Some species are migratory.

Contents 1 Systematics 2 Morphology 3 Diet and feeding 4 Genera 4.1 Fossil record 5 Footnotes 6 References 7 External links

Systematics

The accipitrids have been variously divided into some 5–10 subfamilies. Most share a very similar morphology, but many of these groups contain taxa which are more aberrant. These are placed in their respective position more for lack of better evidence than anything else. It is thus not very surprising that the phylogenetic layout of the accipitrids has always been a matter of dispute.

As mentioned above, the accipitrids are recognisable by a peculiar rearrangement of their chromosomes. Apart from this, morphology and mtDNA cytochrome b sequence data gives a confusing picture of these birds' interrelationships. What can be said is that the hawks, kites, eagles and Old World vultures as presently assigned in all likelihood do not form monophyletic groups:

According to the molecular data, the Buteoninae are most likely poly- or paraphyletic, with the true eagles, the sea eagles, and the buteonine hawks apparently representing distinct lineages. These appear to form a group with the Milvinae, Accipitrinae and Circinae but the exact relationships between the lineages are not at all robustly resolvable with the present data. The Perninae and possibly the Elaninae are older lineages, as are the Old World vultures. The latter are fairly likely also poly- or paraphyletic, with some aberrant species like the Bearded and Egyptian Vultures standing apart from the naked-necked "(not so)true" vultures.^[2]

Morphology

Portrait of a Bald Eagle showing its strongly hooked beak and the cere covering the base of the beak.

The Accipitridae are a diverse family with a great deal of variation in size and shape. They range in size from the tiny Pearl Kite and Little Sparrowhawk, both of which are 23 cm in length and weigh about 85 g, to the Cinereous Vulture, which measures 108 cm and weighs 10 kg. Until the 14th century even these were surpassed by the extinct Haast's Eagle of New Zealand, which is estimated to have weighed 14 kg.^[3] Most Accipitridae exhibit sexual dimorphism in size, although unusually for birds it is the females that are larger than the males.^[4] This sexual difference in size is more pronounced in active species that hunt birds, and is less pronounced in rodent hunters, and almost non-existent in carrion or snail eaters.

The beaks of accipitrids are strong, hooked (sometimes very hooked, as in the Hook-billed Kite or Snail Kite). In some species there is a notch or 'tooth' in the upper mandible. In all accipitrids the base of the upper mandible is covered by a fleshy membrane called the cere which is usually yellow in colour. The tarsi of different species vary by diet, those of bird hunting species like sparrowhawks are long and thin, while species that hunt large mammals have much thicker, stronger ones, and snake-eagle have thick scales to protect from bites.

The plumage the Accipitridae can be striking but rarely utilises bright colours; most birds use combinations of grey, buff and brown.^[5] Overall they tend to be paler below, which helps them seem less conspicuous when seen from below. There is seldom sexual dimorphism in plumage, when it occurs the males are brighter or the females resemble juveniles. In many species juveniles have a distinctly different plumage. Some accipitrids mimic the plumage patterns of other hawks and eagles. They may attempt to resemble a less dangerous species to fool prey, or instead resemble a more dangerous species in order to reduce mobbing by other birds.^[6] Several species of accipitrid have crests used in signalling, and even species without crests can raise the feathers of the crown when alarmed or excited. In contrast most of the Old World vultures possess bare heads without feathers; this is thought to prevent soiling on the feathers and aid in thermoregulation.^[7]

The senses of the Accipitridae are adapted to hunting (or scavenging), and in particular their vision is legendary. The sight of some hawks and eagles is up to 8 times better than that of humans. Large eyes with two fovea provide binocular vision and a "hawk eye" for movement and distance judging. In addition have the largest pectens of any birds. The eyes are tube shaped and cannot move much in their sockets. In addition to excellent vision many species have excellent hearing, but unlike in owls sight is generally the principal sense used for hunting. Hearing may be used to locate prey hidden in vegetation, but sight is still used to catch the prey. Like most birds the Accipitridae generally have a poor sense of smell; even the Old World vultures make no use of the sense, in contrast to the New World vultures in the family Cathartidae.

Diet and feeding

The Palm-nut Vulture is an unusual frugivorous accipitrid , but will also consume fish, particularly dead fish.

Shikra Accipiter badius in Hyderabad, India.

Oriental Honey-buzzard Pernis ptilorhyncus

Accipitrids are predominately predators and most species actively hunt for their prey. A few species may opportunistically feed on fruit and in one species, the Palm-nut Vulture, it forms the major part of the diet.^[8] However other animals form the bulk of the diet of most species. Insects are taken exclusively by around 12 species, in great numbers by 44 additional species, and opportunistically by many others. The Snail Kite and Hook-billed Kites are specialists in consuming snails. Bazas and forest hawks in the genus Accipiter may take reptiles from trees whilst other species hunt them on the ground. Snakes in particular are targeted by the snake-eagles (Circaetus) and serpent-eagles (Spilornis and Dryotriorchis).

Genera

• Subfamily Elaninae - elanid kites (8 species)
  • Genus Elanus
  • Genus Chelictinia
  • Genus Gampsonyx
  • Genus Elanoides
• Subfamily Perninae - honey-buzzards (c.14 species)
  • Genus Aviceda
  • Genus Henicopernis
  • Genus Pernis
  • Genus Leptodon
  • Genus Chondrohierax
  • Genus Machaerhamphus (Doubtfully placed^[9])
• Subfamily Aegypiinae - Old World vultures
  • Genus Sarcogyps
  • Genus Aegypius
  • Genus Torgos
  • Genus Trigonoceps
  • Genus Gyps
  • Genus Necrosyrtes
• Subfamily Gypaetinae^[9]
  • Genus Neophron
  • Genus Gypohierax
  • Genus Gypaetus
  • Genus Eutriorchis^[9]
• Subfamily Buteoninae - buteonine hawks, true eagles and sea-eagles (c.100 living species, probably poly- or paraphyletic)
  • Genus Geranoaetus
  • Genus Buteo (probably paraphyletic, might include Leucopternis in part and Parabuteo)
  • Genus Parabuteo
  • Genus Buteogallus (probably paraphyletic, might include Leucopternis in part)
  • Genus Busarellus
  • Genus Leucopternis (probably polyphyletic)
  • Genus Kaupifalco
  • Genus Butastur
  • Genus Harpyhaliaetus
  • Genus Geranospiza
• Subfamily Aquilinae^[9]
  • Genus Spizaetus
  • Genus Lophaetus (possibly junior synonym of Ictinaetus)
  • Genus Stephanoaetus
  • Genus Polemaetus
  • Genus "Hieraaetus"
  • Genus Aquila (paraphyletic)
  • Genus Ictinaetus
• Subfamily Circinae - harriers (some 16 living species)
  • Genus Circus
• Subfamily Polyboroidinae - harrier hawks
  • Genus Polyboroides^[9]
• Subfamily Milvinae - milvine kites (some 14 species)
  • Genus Harpagus
  • Genus Ictinia
  • Genus Rostrhamus
  • Genus Helicolestes - formerly included in Rostrhamus
  • Genus Haliastur
  • Genus Milvus
  • Genus Lophoictinia
  • Genus Hamirostra
• Subfamily Accipitrinae - goshawks, sparrowhawks, and relatives (c.55 living species)
  • Genus Accipiter
  • Genus Urotriorchis
  • Genus Erythrotriorchis
  • Genus Megatriorchis
• Subfamily Circaetinae - snake-eagles (about one dozen species)
  • Genus Terathopius
  • Genus Circaetus
  • Genus Spilornis
  • Genus Pithecophaga^[9]
• Subfamily Haliaeetinae^[9]
  • Genus Haliaeetus
  • Genus Ichthyophaga
• Subfamily Harpiinae^[9]
  • Genus Morphnus
  • Genus Harpia
  • Genus Harpyopsis
  • Genus Harpagornis
• Subfamily Melieraxinae^[9]
  • Genus Melierax (Micronisus)

Fossil record

Like with most other birds of prey, the fossil record of this group is fairly decent from the latter Eocene onwards (c.35 mya), with modern genera being well documented since the Early Oligocene, or around 30 mya.

• Milvoides (Late Eocene of England)
• Aquilavus (Late Eocene/Early Oligocene - Early Miocene of France)
• Palaeocircus (Late Eocene/Early Oligocene of France)
• Palaeastur (Agate Fossil Beds Early Miocene of Sioux County, USA)
• Pengana (Early Miocene of Riversleigh, Australia)
• Promilio (Agate Fossil Beds Early Miocene of Sioux County, USA)
• Proictinia (Early - Late Miocene/Early Pliocene of C and SE USA)
• Neophrontops (Early/middle Miocene - Late Pleistocene) - formerly in Neophron
• Mioaegypius (Xiacaowan middle Miocene of Sihong, China)
• Apatosagittarius (Late Miocene of Nebraska, USA)
• Palaeoborus (Miocene)
• Qiluornis (Miocene of Shandong, China)
• Thegornis (Miocene of Argentina)
• Garganoaetus (Early Pliocene of Gargano Peninsula, Italy)
• Amplibuteo (Late Pliocene of Peru - Late Pleistocene of S North America and Cuba) - may belong to extant genus Harpyhaliaetus
• Neogyps
• Palaeohierax - includes "Aquila" gervaisii
• Wetmoregyps - formerly Morphnus daggetti

Accipitrids are known since Early Eocene times, or about from 50 mya onwards, in fact, but these early remains are too fragmentary and/or basal to properly assign a place in the phylogeny. Likewise, as remarked above, molecular methods are of limited value in determining evolutionary relationships of and within the accipitrids. What can be determined is that in all probability, the group originated on either side of the Atlantic, which during that time was only 60-80% its present width. On the other hand, as evidenced by fossils like Pengana, some 25 mya, accipitrids in all likelihood rapidly acquired a global distribution - initially probably even extending to Antarctica.

• Accipitridae gen. et sp. indet. (Huerfano Early Eocene of Huerfano County, USA)^[10]
• Accipitridae gen. et sp. indet. (Borgloon Early Oligocene of Hoogbutsel, Belgium)^[11]
• Accipitridae gen. et sp. indet. (Bathans Early/Middle Miocene of Otago, New Zealand)^[12]
• "Aquila" danana (Snake Creek Late Miocene/Early Pliocene of Loup Fork, USA) - formerly also Geranoaetus or Buteo
• Accipitridae gen. et sp. indet. (Early/Middle Pliocene of Kern County, USA) - Parabuteo?^[13]
• Accipitridae gen. et sp. indet. (Late Pliocene/Early Pleistocene of Ibiza, Mediterranean) - Buteo?^[14]
• Accipitridae gen. et sp. indet. (Egypt)

Specimen AMNH FR 2941, a left coracoid from the Late Eocene Irdin Manha Formation of Chimney Butte (Inner Mongolia) was initially assessed as a basal mid-sized "buteonine"^[15]; it is today considered to be more likely to belong in the Gruiformes genus Eogrus^[16].

Footnotes

1. ^ de Boer (1975), Amaral & Jorge (2003), Federico et al. (2005)
2. ^ Wink et al. (1996)
3. ^ Brathwaite (1992)
4. ^ Paton et al. (1994)
5. ^ Thiollay (1994)
6. ^ Negro (2008)
7. ^ Ward et al.(2008)
8. ^ Although not the entire diet. Thomson et al. 1957
9. ^ ^{a b c d e f g h i} Lerner & Mindell, 2005
10. ^ Specimen AMNH FR 7434: Left carpometacarpus of a Snail Kite-sized bird: Cracraft (1969)
11. ^ Tarsometatarsus of a bird the size of an Eurasian Sparrowhawk: Smith (2003)
12. ^ Specimens MNZ S42490, S42811: Distal left tibiotarsus and distal right ulna of a bird the size of a smallish eagle: Worthy et al. (2007)
13. ^ Distal tibia quite similar to Harris's Hawk: Miller (1931)
14. ^ Alcover (1989)
15. ^ Wetmore (1934)
16. ^ AMNH (2007)

References

• Alcover, Josep Antoni (1989): Les Aus fòssils de la Cova de Ca Na Reia ["The fossil birds of Ca Na Reia cave"]. Endins 14-15: 95-100. [Catalan with English abstract]
• Amaral, Karina Felipe & Jorge, Wilham (2003): The chromosomes of the Order Falconiformes: a review. Ararajuba 11(1): 65-73. PDF fulltext
• American Museum of Natural History (AMNH) (2007): AMNH FR 2941 specimen information. Retrieved 2008-APR-22.
• Brathwaite, D. H. (1992): "Notes on the weight, flying ability, habitat, and prey of Haast's Eagle (Harpagornis moorei)". Notornis 39(4): 239–247.
• Cracraft, Joel (1969): Notes on fossil hawks (Accipitridae). Auk 86(2): 353-354. PDF fulltext
• de Boer, L.E.M. (1975): Karyological heterogeneity in the Falconiformes (Aves). Cellular and Molecular Life Sciences 31(10): 1138-1139. doi:10.1007/BF02326755 (HTML abstract)
• Federico, Concetta; Cantarella, Catia Daniela; Scavo, Cinzia; Saccone, Salvatore; Bed'Hom, Bertrand & Bernardi, Giorgio (2005): Avian genomes: different karyotypes but a similar distribution of the GC-richest chromosome regions at interphase. Chromosome Research 13(8): 785-793. doi:10.1007/s10577-005-1012-7 (HTML abstract)
• Lerner , Heather R.L. & David P. Mindell (2005): Phylogeny of eagles, Old World vultures, and other Accipitridae based on nuclear and mitochondrial DNA. Molecular Phylogenetics and Evolution 37:327–346 PDF fulltext
• Miller, Loye H. (1931): Bird Remains from the Kern River Pliocene of California. Condor 33(2): 70–72. PDF fulltext
• Negro, J.J. (2008) Two aberrant serpent-eagles may be visual mimics of bird-eating raptors Ibis 150 (2): 307–314 doi:10.1111/j.1474-919X.2007.00782.x
• Paton, P.W.C.; Messina, F.J. & C.R. Griffin (1994): A Phylogenetic Approach to Reversed Size Dimorphism in Diurnal Raptors. Oikos 71 (3): 492-498
• Smith, Richard (2003): Les vertébrés terrestres de l'Oligocène inférieur de Belgique (Formation de Borgloon, MP 21): inventaire et interprétation des données actuelles. [Early Oligocene terrestrial vertebrates from Belgium (Borgloon Formation, MP 21): catalog and interpretation of recent data.] Coloquios de Paleontología E1: 647-657. [French with English abstract] PDF fulltext
• Thiollay, J.M. (1994): Family Accipitridae (Hawks and Eagles) in del Hoyo, J.; Elliot, A. & Sargatal, J. (editors). (1994). Handbook of the Birds of the World. Volume 2: New World Vultures to Guineafowl. Lynx Edicions. ISBN 8487334156
• Thomson, A.L. & R. E. Moreau (1957) : Feeding habits of the palm-nut vulture Gypoheerax. Ibis 99 (4) , 608–613 doi:10.1111/j.1474-919X.1957.tb03053.x
• Ward, J.; McCafferty, D.; Houston, D.; Ruxton, G. (2008). "Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation". Journal of Thermal Biology 33 (3): 168-173 doi:10.1016/j.jtherbio.2008.01.002
• Wink, M.; Heidrich, P. & Fentzloff, C. (1996): A mtDNA phylogeny of sea eagles (genus Haliaeetus) based on nucleotide sequences of the cytochrome b gene. Biochemical Systematics and Ecology 24: 783-791. doi:10.1016/S0305-1978(96)00049-X PDF fulltext
• Worthy, Trevor H.; Tennyson, A.J.D.; Jones, C.; McNamara, J.A. & Douglas, B.J. (2007): Miocene waterfowl and other birds from central Otago, New Zealand. J. Syst. Palaeontol. 5(1): 1-39. doi:10.1017/S1477201906001957 (HTML abstract)
• Wetmore, Alexander (1934): Fossil birds from Mongolia and China. American Museum Novitates 711: 1-16. PDF fulltext

External links

Wikimedia Commons has media related to: Accipitridae

• American Museum of Natural History: Accipitridae AMNH 7434 Specimen Data. Retrieved 2007-FEB-10.
• Accipitridae videoson the Internet Bird Collection
• xeno-canto.org: Accipitridae sounds. Retrieved 2006-DEC-01.

v • d • e Order: Accipitriformes Family Sagittaridae (Secretarybird) • Pandionidae (Osprey) • Accipitridae (Buzzards, eagles, harriers, hawks, kites, and Old World vultures) • Cathartidae (New World vultures)

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)