Accipitridae

Members of this extremely diverse family are superbly well adapted for life as raptors, with features such as a sharp, hooked bill and strong jaw muscles, strong legs and feet with sharp talons, and excellent vision. They include the huge Old World vultures, which spend hours soaring at great heights in search of carrion; the small, fast-flying accipiters, which hunt birds in forest habitats; and the most powerful avian predators of all, the monkey-eating eagles.

Additional information

Females are larger than males. At one end of the scale is the petite male Pearl Kite (Gampsonyx swainsonii) of South America, which weighs just 80g, while at the other is the huge female Himalayan Griffon (Gyps himalayensis), at 12kg. The group is equally diverse in their overall body structure, according to hunting style and primary prey. This variation is manifested in bill structure; wing and tail shape; and leg, toe, and talon length and development.

The majority of raptors are solitary, but live in pairs during the breeding season. Some are gregarious when food supplies are plentiful; a few are highly social and not only feed in groups but breed in colonies. Some have colonial or semi-colonial roosts outside the breeding season, and some migrate in flocks. Members of the family have a poor sense of smell, so hunt mostly by sight. Old World vultures, unlike their New World counterparts family Cathartidae), locate carcasses by sight or observing the behavior of other birds and animals. A few species practice cooperative hunting, and some engage in kleptoparasitism: stealing the prey caught by other birds or animals.

Many species migrate during the same periods, and large diurnal flights (sometimes of many thousands of individuals) can be observed at traditional sites. Migrants use thermals or prevailing wind to glide so they use less energy. Movements are generally tied to the seasons and the availability of prey; a few species are essentially nomadic, moving according to the abundance of prey and completely evacuating areas once they have become devoid of food. The movements of some species living at high altitudes are closely tied to cyclic prey populations (such as grouse and small rodents); if population densities of these animals crash, it can result in large-scale movements or invasions to lower latitudes.

Most are monogamous, and pair for life. Polygyny is frequently observed in some harrier species (genus Circus), and polyandry is also recorded in Galapagos Hawk (Buteo galapagoensis). Snail Kite (Rostrhamus sociabilis) is known to practice both, serially, to maximize the production of young during periods of abundant food. Nest helpers are reported for Harris's Hawk (Parabuteo unicinctus).

Taxonomy

Number of genera: 64

Number of species: 237

Recent DNA studies have helped resolve relationships mudied by ecological and morphological convergence within the family, and several basic 'types' previously identified by morphology have been found not to be closely related. Based on DNA analysis, 13 subfamilies are now recognized:

• Booted eagles (Aquiliinae)
• Sea eagles (Haliaeetinae)
• Harpy eagles (Harpiinae)
• Snake eagles (Circaetinae)
• Old World vultures (Aegypiinae & Gypaetinae)
• Kites (Milvinae, Perninae & Elaninae)
• Harriers (Circinae)
• Buzzards (Bureoninae)
• Gabor Goshawk (Melierax gabar, Melieraxinae)
• African Harrier-hawk (Polyboroides typus, Polyboroidinae)

 A list of all species can be found here.