8 



Introduction 



and this adaptation is well shown in Hummingbirds. The bare tracts on the 

 nape and along the throat allow the neck to readily lie against the middle of the 

 back, or to bend downward over the points of the breast-bone, while the bare 

 spaces under the wings and along the sides of the body permit the wings to be 

 easily and closely applied to the body, the sides conforming almost exactly to 

 the curve of the edge of the folded wing. The large bare space on the under side, 

 found in nearly all birds save the water fowl, is merely to allow the warmth of 



47481 



v ... < ;:;-' :::: '" ---. 10 



24 23 



FIG. 5. Topography of a bird. (From Coues's " Key.") 



i, forehead (frons); 2, lore; 3, circumocular region; 4, crown (vertex); 5, eye; 6, hind head (occiput}; 7, nape 

 (nucha); 8, hind neck (cervix); 9, side of neck; 10, interscapular region; n, dorsum, or back proper, including 10; 12, 

 nolaum, or upper part of body proper, including 10, n, and 13; 13, rump (vropygium); 14, upper tail-coverts; 15, tail; 

 16, under tail-coverts; 17, tarsus; 1 8, abdomen; 19, hind toe (hallux); 20, gastrceum, including 18 and 24; 21, outer or 

 fourth toe; 22, middle or third toe; 23, side of the body; 24, breast (pectus); 25, primaries; 26, secondaries; 27, tertiaries, 

 nos. 25, 26, 27, are all remiges; 28, primary coverts; 29, alula, or bastard wing; 30, greater coverts; 31, median coverts; 

 32, lesser coverts; 33, the " throat," including 34, 37, and 38; 34, jugulum, or lower throat; 35. auriculars; 36, malar 

 region; 37, gula, or middle throat; 38, mentum, or chin; 39, angle of commissure, or corner of mouth; 40, ramus of under 

 mandible; 41, side of under mandible; 42, gonys; 43, apex, or tip of bill; 44, lomia, or cutting edges of the bill; 45, culmen, 

 or ridge of upper mandible, corresponding to gonys; 46, side of upper mandible; 47, nostril; 48, passes across the bill a 

 little in front of its face. 



the body to be directly applied to the eggs during incubation, and in birds like 

 Ducks and Penguins (also Auks), which are densely or completely feathered 

 beneath, a bare space is present during the breeding season." 



Renewal of Feather Covering. Although a considerable proportion of the 

 feathers in flying birds are relatively strong, especially those of the wings and 

 tail, the more or less active life of their owner results sooner or later in the wear 

 and often injury of all feathers. The chief of the destructive influences to which 

 feathers are subjected are abrasion and fading, the one a mechanical disintegra- 

 tion, and the other a chemical decoloration. Besides these there are other minor 

 factors, such as " the age of a feather, its position, its structure, its color, and the 



