The great majority of Raptorial birds belong to the present family, which comprises Eagles, Buzzards, Kites, Hawks, Harriers, Falcons, and a number of intermediate forms. They are distinguished from the Osprey by having the body-feathers provided with an aftershaft, and from the Vultures by having the head and neck feathered. In virtue of the last character Gypaetus (the Lammergeyer), which is intermediate in characters between the Vultures and Eagles, is here assigned to the neighbourhood of the latter.
Throughout the family there are 12 tail-feathers and 14 cervical vertebrae. Nearly all are carnivorous, a few of the smaller species being insectivorous partly or wholly, and the majority capture living prey. The hair and feathers of the prey, if not removed before eating, are cast up, with the bones, in the form of pellets. As a rule, birds of this family are solitary, and all are monogamous.
Scarcely any two authors agree as to the division of the Falconidae into subfamilies. Sharpe in the ' Catalogue' admits five : Polyborinae, Accipitrinae, Buteoninae, Aquilinae, and Falconinae; but the result is unsatisfactory and artificial. Blyth and Gurney employed far more divisions; the former (' Ibis,' 1863) arranged these birds in 10 subfamilies, the latter in his last work ('A List of the Diurnal Birds of Prey') in no less than 11. If the Falconidae are to be arranged in natural subfamilies at all, this number must, I believe, be increased rather than diminished ; and as I can find no satisfactory system, I think it best to leave the family undivided with the exception of the Lammergeyer, which appears entitled to rank as a subfamily apart.
a. Claws blunt; bill lengthened; a tuft of long bristles on the chin ………………………Gypaetinae, p. 328.
b. Claws sharp; bill not lengthened ; no bristles on chin ………………………Falconinae, p. 330.