THE DIURNAL BIRDS OF PREY HAWKS, EAGLES AND VULTURES 283 



victims, their eyes change from long focus to short 

 focus and the adjustment is so instantaneous that they 

 follow their prey with clear vision. The eyes of hawks 

 are smaller than those of the owls for all the species 

 are diurnal, although some species, like the rough-legged, 

 are most active toward dusk and the tropical laughing 

 falcons can be heard long after dark. Hawks* eyes vary 

 in color from yellow to red, some being gray and others 

 brown. Young birds usually have different colored eyes 

 from the adults, those of the Cooper's hawk, for ex- 

 ample, changing with maturity from yellow to bright red. 

 The voices of hawks, for the most part, are harsh dis- 

 cordant screams, quite in keeping with their wild natures. 

 The short winged species like the sharp-shinned and 

 Cooper's hawks, that lie in wait for their prey, are usually 

 silent except on their nesting grounds, but the others 

 call frequently as though to strike fear in their quarry. 



THE HOME OF THE BLACK VULTURE 



No nest is built, the eggs being laid on the ground beneath a log or 

 boulder. This bird was nesting on Ancon Hill, Canal Zone, Panama. 



There are four families of hawks found in North 

 America but, with the exception of the vultures, they may 

 well be considered together. The family Buteonidae in- 

 cludes the majority of the hawks which are variously 

 known as the broad-winged hawks, also called buzzards 

 in Europe, kites, harriers, eagles, goshawks, etc. The 

 family Falconidae includes the falcons and the caracaras, 

 the latter being degenerate falcons that have become large- 

 ly vulturine in their habits. The family Pandionidae in- 

 cludes only the fish hawks or ospreys which differ from 

 other hawks in having one toe reversible so that a better 

 fish gaff may be formed. The family of vultures, Cath- 

 artidae, are degenerate hawks having naked heads and 

 weak feet, that feed almost entirely upon carrion. 

 The Vultures (Family Cathartidae). 



There are nine species in the family Cathartidae, con- 

 fined entirely to the New World. The Old World vul- 



A LONG-WINGED HAWK THE MARSH HAWK 



The Marsh hawk seldom alights in trees, but usually has an exposed 

 stub from which he can keep a lookout near his nest. The Marsh hawk 

 occasionally takes marsh birds or young ducks, but usually feeds upon 

 mice and frogs. 



tures, although very similar in general appearance, are 

 put in a different family. In North America there are 

 but three species and one of these, the California vul- 

 ture, is nearing extinction because of the poisoning of 

 carcasses by rangers to kill wolves and coyotes. This is 



Photograph by Herbert K. Job 



COOPER'S HAWK ON NEST IN HEMLOCK FROM ABOVE 



This is one of the short-winged, long-tailed hawks which are so destruc- 

 tive to birds and poultry. With the sharp-shinned and goshawk they 

 account for 90 per cent of the depredations on the poultry yard. 



