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Griffon vulture

Birds of prey, or raptors, include species of bird that primarily hunt and feed on vertebrates that are large relative to the hunter. Additionally, they have keen eyesight for detecting food at a distance or during flight, strong feet equipped with talons for grasping or killing prey, and powerful, curved beaks for tearing flesh.[2][3][4] The term raptor is derived from the Latin word rapio, meaning to seize or take by force.[5] In addition to hunting live prey, most also eat carrion, at least occasionally, and vultures and condors eat carrion as their main food source.[2]

Although the term bird of prey could theoretically be taken to include all birds that primarily consume animals,[4] ornithologists typically use the narrower definition followed in this page. Examples of animal-eating birds not encompassed by the ornithological definition include storks, herons, gulls, skuas, penguins, kookaburras, and shrikes, as well as the many songbirds that are primarily insectivorous.

Common names


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.

  • Eagles tend to be large birds with long, broad wings and massive feet. Booted eagles have legs and feet feathered to the toes and build very large stick nests.
  • Ospreys, a single species found worldwide that specializes in catching fish and builds large stick nests.
  • Kites have long wings and relatively weak legs. They spend much of their time soaring. They will take live vertebrate prey, but mostly feed on insects or even carrion.
  • The true hawks are medium-sized birds of prey that usually belong to the genus Accipiter
  • Buzzards are medium-large raptors with robust bodies and broad wings, or, alternatively, any bird of the genus Buteo
  • Harriers are large, slender hawk-like birds with long tails and long thin legs. Most use a combination of keen eyesight and hearing to hunt small vertebrates, gliding on their long broad wings and circling low over grasslands and marshes.
  • Vultures are carrion-eating raptors of two distinct biological families: the Accipitridae, which occurs only in the Eastern Hemisphere; and the Cathartidae, which occurs only in the Western Hemisphere. Members of both groups have heads either partly or fully devoid of feathers.
  • Falcons are medium-size birds of prey with long pointed wings. They belong to the Falconidae family, rather than the Accipitridae
  • Caracaras are a distinct subgroup of the Falconidae unique to the New World, and most common in the Neotropics – their broad wings, naked faces and appetites of a generalist suggest some level of convergence with either the Buteos or the vulturine birds, or both.
  • Owls are variable-sized, typically night-specialized hunting birds. They fly almost silently due to their special feather structure that reduces turbulence. They have particularly acute hearing.

Many of these English language group names originally referred to particular species encountered in Britain. As English-speaking people travelled further, the familiar names were applied to new birds with similar characteristics. Names that have generalised this way include: kite (Milvus milvus), sparrow-hawk 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): merlin (Falco columbarius), osprey (Pandion haliaetus).

Systematics


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

Louis Pierre Veillot used additional ranks: order, tribe, family, genus, species. Birds of prey (order Accipitres) were divided into diurnal and nocturnal tribes; the owls remained monogeneric (family Ægolii, genus Strix), whilst the diurnal raptors were divided into three families: Vulturini, Gypaëti, and Accipitrini.[6]

Thus Veillot's families were similar to the Linnaean genera, with the difference that shrikes were no longer included amongst the birds of prey.

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 the accipitrid species.[7] The phylogeny of Accipitriformes is complex and difficult to unravel. Widespread paraphylies were observed in many phylogenetic studies.[8][9][10][11][12] More recent and detailed studies show similar results.[13] 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 the clade containing Aquilinae and Harpiinae).[7]

The diurnal birds of prey are formally classified into five families of two orders.

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 separately in an enlarged stork family, Ciconiiformes, and may be raised to an order of their own, Cathartiiformes.

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 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.[14][15][16] The orders in bold text are birds of prey orders; this is to show the polyphly of the group as well as their relationships to other birds.

Migration


Migratory behaviour evolved multiple times within accipitrid raptors.

The earliest event occurred nearly 14 to 12 million years ago.

Migratory species of raptors had a southern origin because it seems that all of the major lineages within Accipitridae had an origin to one of 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.[7] Similar results of southern origin in other taxonomic groups can be found in the literature.[17][18][19]

Distribution and biogeographic history highly determine the origin of migration in birds of prey.

A recent study discovered new connections between migration and the ecology, life history of raptors.

Sexual dimorphism


Raptors are known to display patterns of sexual dimorphism. It 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 a great deal of data is required.[21]

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.[22] It has also been proposed that sexual dimorphism 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.[23]

In non-predatory birds, males are typically larger than females.

See also


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