Bird
of prey or predatory bird, also known as raptors, refers to several species of birds
that hunt and feed on rodents and other small animals. The term raptor is derived from the Latin
word rapere, meaning to seize or take by force.
These birds are characterized by keen
vision that allows
them to detect their prey during flight and powerful talons and beaks.
Taken literally,
the term bird of prey has
a wide meaning that includes many birds that hunt and feed on animals and also
birds that eat very small insects. In ornithology, the definition for "bird of
prey" has a narrower meaning: birds
that have very good eyesight for finding food, strong feet for holding food, and a strong
curved beak for tearing flesh. Most birds of prey also have strong
curved talons for catching or killing prey. An example of this
difference in definition, the narrower definition excludes storks and gulls, which can eat quite large fish, partly
because these birds catch and kill prey entirely with their beaks, and
similarly bird-eating skuas, fish-eating penguins, and vertebrate-eating kookaburras are excluded. Birds of prey
generally prey on vertebrates, which are usually quite large relative to the size of the
bird. Most also eat carrion, at least occasionally, and
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. The phylogeny of Accipitriformes is complex and
difficult to unravel. Widespread paraphylies were observed in many phylogenetic
studies.[6][7][8][9][10] 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 the clade
containing Aquilinae and Harpiinae).
- Accipitridae: hawks, eagles, buzzards, harriers, kites, and Old World vultures
- Pandionidae: the osprey
- Sagittariidae: the secretarybird
- Falconidae: falcons, caracaras, and forest falcons
- Cathartidae: New World vultures
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:
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. The phylogeny of Accipitriformes is complex and
difficult to unravel. Widespread paraphylies were observed in many phylogenetic
studies.[6][7][8][9][10] 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 the clade
containing Aquilinae and Harpiinae).
- Accipitridae: hawks, eagles, buzzards, harriers, kites, and Old World vultures
- Pandionidae: the osprey
- Sagittariidae: the secretarybird
- Falconidae: falcons, caracaras, and forest falcons
- Cathartidae: New World vultures
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:
Historical
classifications
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
Turnton.
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.
Thus Veillot'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), Veillot 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).
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 (see below). They are mainly woodland birds that hunt by sudden dashes from a concealed perch. They usually have long tails for tight steering.
- Buzzards are medium-large raptors with robust bodies and broad wings, or, alternatively, any bird of the genus Buteo (also commonly known as "hawks" in North America).
- 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 only occurs in the Eastern Hemisphere; and the Cathartidae, which only occurs 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 pointy wings. They belong to the Falconidae family, rather than the Accipitridae (accipiters). Many are particularly swift flyers.
- 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).
The earliest
event occurred nearly 14 to 12 million years ago. This result seems to be one
of 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 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. 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
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 publish paper shows that
"clutch size and hunting strategies have been proved to be 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 the
question: why species winters at one location while the others are elswhere. It
is interesting that how temperature and precipitation related factors differs
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 consevational consequences in the
protection of migratory raptors.
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.
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 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, 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 the
nest and hunting. Larger females are favored because they can incubate larger
numbers of offspring, while also being able to breed a larger clutch size