146 FALCONIFORMES 



CHAP. 



Fam. IV. Falconidae. This group may be divided into the 

 Sub- families (1) Gypaetinae for the Lammergeiers ; (2) Polyhorinae 

 for the " Carrion Hawks " ; (3) Accipitrinae for the Hawks, with 

 Circus, P.olyhoro'idcs, and so forth ; (4) Aquilinae for the Eagles ; 

 (5) Buteoninae for the Buzzards and Kites; and (6) Falconinae 

 for the Falcons. 



Tliough the skull is small in Circus and some other forms, it 

 is usually large and broad, being considerably elongated in the 

 Aquilinae. The short stout bill is strongly curved, and ter- 

 minates in a hook, which is often nearly perpendicular, and is 

 specially prominent in Bostrliamus, Leptodon, Harpyludiactus, 

 Pithecophaga and Thrasaetus ; the basal third is straight in Eagles, 

 while the edges of the maxilla are lobed or festooned to a variable 

 extent, and in the Falconinae are distinctly toothed, or even biden- 

 tate in the case of Spiziapteryx, Harpagus, and Baza. A bony 

 ridge over the eye conduces to the jfierce aspect, especially in the 

 larger species. The feet are robust and well-fitted for grasping, 

 and are enormously developed in Thrasaetus ; the metatarsus is 

 much flattened, and may be scutellated or reticulated, though the 

 scales are usually smaller behind; the tibia generally exceeds it 

 in measurement, but in Accipitrine forms is nearly equal, giving 

 them a long-legged appearance. Elongated bare metatarsi are 

 characteristic of Circus, Polyhoro'idcs, and the Polyborinae. The 

 claws are sharp and curved, especially in Bostrhamus ; a short 

 membrane connects the middle and outer toes, and the inner also 

 in the Polyborinae; while their under surface is more or less padded, 

 and exhibits rugose spicules below in Busarellus, similar to those 

 in PoMdion. The powerful wings may be long and pointed, as in 

 the Kites, Falcons, and Harriers ; moderate and somewhat rounded, 

 as in the Eagles and Buzzards ; or short and narrow, as in Hawks. 

 Falconers term the long- winged forms " iioble," the short-winged 

 " ignoble." The tail, usually of medium size, but sometimes very 

 short, as in Helotarsus and Gypohierax, is decidedly elongated in 

 the Accipitrinae and Polyhorus, and also in Milvus, Loplioictinia, 

 Elano'ides, and Nauclerus, where it is forked- very deeply in the 

 two last : it may be wedge-shaped, as in Uroaetus, Thalassaetus, 

 Harpyhaliaetus, and Gypaetus ; rounded, as in Elanus and Hcdi- 

 aetus ; nearly even, as in Buteo and Aquila; or emarginated, as in 

 Ictinia and Bostrhamus. ^Normally there are twelve rectrices, but 

 Thalassaetus has fourteen. The colour varies greatly witli age. 



