JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 17 



The Tarsus, which is measured from the bend of the leg (end of 

 tibia ) to the roots of the toes (C to D in illustration ) , is an important 

 factor in the identification of many species. The feet are very variable 

 in shape and arrangement of the toes. These variations are of the 

 greatest importance, representing generic and, often, family differences. 



The Toes are usually three or four (the Ostrich has but two), 

 the greater number having three in front and one behind; sometimes 

 two in front and two behind (Zygodactyle); two in front and one 

 behind; or, in one family (not North America), all four turned for- 

 ward. Some families have the outer and middle toes joined or fused 

 together for part of their length (Syndactyle), as in the Kingfisher. 

 Some species have webbed feet, others have the toes armed with 

 curved talons, and so on; but the various differences with which we 

 wish to become familiar can better be illustrated than described. 



Foot of Sparrow 



Foot of three-toed Woodpecker Types of Feet. Land Birds. 



THE BILL. 



The Bill consists of an upper and a lower mandible, both of which 

 are movable. The shape is of great assistance in determining the 

 family to which the species belong. Four principal types are recog- 

 nized : 



i. Epignathous. Upper mandible longer than lower; the tip 

 bent or hooked over the end of lower mandible. (Examples: Hawks, 

 Gulls, Petrels, Parrots. ) 



