I 9 40 THE DIURNAL BIRDS OF PREY 



oil gland is crowned with a circle of feathers. Inferiorly the windpipe is provided 

 with an organ of voice. Although very closely connected by the lammergeier, the 

 falcons and their allies differ from the vultures (except the lammergeier) by the 

 head being clothed with true feathers, and by the size of the females exceeding that 

 of the males. The group includes the smallest members of the order, while its 

 largest representatives are second only in size to the vultures. As a rule, these 

 birds subsist mainly or exclusively on prey killed by themselves, although some will 

 eat carrion, and a few feed on honeycomb. L,ike other Accipitrines, the two sexes 

 associate in pairs, which mate for life, while the number of young produced in a 

 brood seldom exceeds four, and is frequently less. They have a cosmopolitan dis- 

 tribution and may be divided into five subfamilies. 



The true falcons, as represented by the peregrine and the kestrel, 

 are the typical members of a subfamily, characterized by the length of 

 the tibia being considerably greater than that of the metatarsus, by the scutes on 

 the hinder aspect of the metatarsus being arranged in a reticulate manner, and by 

 the sides of the bill being notched. In all of them the cere is large, and often 

 brightly colored. With regard to the extent of the genus Falco, there is a certain 

 amount of difference of opinion among ornithologists, some including in it the 

 whole of the European falcons, while others separate the gerfalcons (as Hierofalco}, 

 and the kestrels (as Tinnunculus, or Cerchneis}. Used in the wider sense, the genus 

 will include (with the exception of one peculiar species from the Argentine and 

 another from New Zealand) all the falcons in which the nostrils are circular and 

 furnished with a distinct tubercle in the middle. The beak in all is short and 

 curved, with one notch in the upper mandible; the wings are long and pointed, with 

 the first and third quills of equal length, and the second the longest, and the toes 

 are elongated. Many of the larger species have a distinct dark stripe on the cheek, 

 which in the peregrine expands into a large patch. All are subject to great varia- 

 tion of plumage, according to age~ which renders the discrimination of many of the 

 species a matter of exceeding difficulty. 



Under the common title of gerfalcons are included several closely- 

 allied falcons of large size, from the northern regions of the Northern 

 Hemisphere, distinguished by the comparative shortness of the toes, more especially 

 the fourth, which (exclusive of the claw) is about equal in length to the second. 

 The wings, moreover, are rather short, and the length of the interval between the 

 tips of the primary and secondary quills does not exceed half the length of the tail. 

 The beak is somewhat elongated, and the color of the plumage tends to slaty gray, 

 or white, these being the only falcons in which there is such a type of coloration. 

 One of the best known of these species is the Greenland falcon (Falco candicans} , of 

 Greenland and North America, young birds occasionally straggling to the British 

 Islands. This is the lightest-colored member of the group, and is hence sometimes 

 termed the white gerfalcon. Its distinctive characteristics are to be found in the 

 yellow tint of the cere, beak, and claws, and by the ground color of the plumage 

 being white at all ages. In old birds, the head, under parts, and tail become almost, 

 or completely, white; while the upper parts retain small black spots. In the young 

 the breast and flanks are longitudinally streaked with brown. The length of the 



