THE WORLD'S BIRDS. 51 



Form. — Bill variable in form, but generally of medium 

 length, and . flat-sided, with nostrils slit-like and 

 generally far forward, corner of mouth below eye ; 

 feet with shanks of variable length, front toes 

 usually fully webbed, though in some the webbing 

 is very slight ; hind- toe usually very small. Wings 

 long and pointed ; tail moderate or long. Head 

 large, and body light. 



Plumage and Colouration. — Colouration usually 

 showing much white in adults ; no sex-difference, but 

 often a seasonal change. Young usually mottled 

 brown, and very unlike adults. Beak and feet 

 usually bright-coloured. 



Young. — Downy and rather active, but the food is 

 disgorged for them by their parents, though they 

 can pick it up. Their down is usually grey, with 

 dark spots. 



Nest. — A loose, open structure of sticks, sea-weed, 

 etc., placed on the ground, on rock-ledges, or on 

 trees and bushes. 



Eggs. — One to four ; spotted. 



Incubation. — Three to four weeks. 



Courtship. — Very demonstrative, the male arching 

 his neck, or lowering it with the head turned up, 

 and opening his wings at the pinions, while keeping 

 them closed at the tip. 



Food. — Fish, and other marine animals ; carrion, 

 mice, insects and berries are eaten by many 

 species ; they also often eat the eggs and young 

 of other birds. Indigestible substances are dis- 

 gorged as " castings." 



Gait. — The typical gulls walk easily and gracefully, 

 but some of the short-legged Terns waddle, and 

 walk but little. They swim lightly, but hardly 

 any can dive. Many of them perch on trees. 



Flight. — Slow, but graceful, and long-sustained. The 

 Skuas and Noddies fly with quicker strokes. 



A* 



