The Audubon Societies 223 



It hardly seemed true that a film of snow rested on the upper slopes of 

 nearby mountains, or that early morning saw a thin hoar-frost on the hill 

 farms. As yet the chill of late winter was not broken, but the birds knew, and 

 the trees and the shrubs knew, as well as the bUthe chipmunks and frogs, 

 that May had come. — A. H. W. 



THE PLAN OF A BIRD. PART II 



In the January-February issue of this year, we began a study of structure 

 and adaptation. After defining in simple terms what a vertebrate is and what 

 a bird is, we took up a few points about flight in general, applying some of the 

 principles of flight to the flying mechanism found in birds. We discovered that 

 some birds cannot fly, that some swim better than they fly, and that most 

 birds do not depend entirely upon the power of flight to find food. Comparing 

 the fore-Kmbs or wings of a bird with the hind-limbs or legs, we saw, also, 

 that the former have almost without exception been specialized for the pur- 

 pose of flight. 



In this exercise, let us try to find out some of the uses to which the hind- 

 Hmbs are put, and, in order to do this most successfully, we will forget for the 

 moment that birds can fly. 



Do any of you recall a game of birds called "avelude," in which birds are 

 divided into scratchers, runners, climbers, perchers, waders, swimmers, birds 

 of prey, and so on? This game in reality illustrates a once popular scheme of 

 classification, based largely upon the uses of the legs and feet of birds. From 

 the above category, it will be seen that these uses are numerous. 



If we stop to think where birds find their food and where they nest — the 

 two principal occupations of their lives — we can more readily understand the 

 variety of uses to which their hind-Umbs are put. All parts of trees and shrubs, 

 all kinds of moist and dry ground vegetation, the smooth beach, pebbly shore, 

 and inland waterways, even the air and sea, offer feeding-places to birds, 

 while they find nesting-sites in precarious positions from barren rock- 

 cliffs to semi-floating water-weeds and rushes. Watch the birds about you, 

 and discover for yourselves the great variety of uses to which their legs and 

 feet are put. 



The Woodpecker seeks its food along the bark of tree trunks, and must be 

 able to hold itself in such a position that it can get this food, and so we find 

 it with curiously yoke-toed feet (two toes bending forward and two backward) 

 clinging safely and securely against the trunk, while it delivers blows of much 

 force on the stubborn bark. Most Sandpipers confine themselves to shore- 

 Hnes, as Herons do to low- tide areas and marshes, so we may look for long legs 

 and toes fitted to bear the weight of the bird most successfully in these places. 

 Perching birds must have a strongly clasping foot, but not so strong as the 

 grasping foot of birds of prey. Water and air loving species do not need long 



