43 6 



The Bird 



body between the thighs. Both sexes are provided with 

 this contrivance during the breeding season, and relieve 

 each other of the burden at intervals. 



" The gull tribe, however, are far more exposed to acci- 

 dent and to enemies, both in adult life and as to their 

 eggs and young, than are the penguins, petrels, and others 

 mentioned above; and here the rule is from two (skuas) 

 to four (gulls and terns) eggs in a nest. When we come 



FIG. 346. Eggs of Ostrich, Cassowary, Hummingbird, and Hen, 

 showing comparative size. 



to the shore- and marsh-birds the plovers, snipe, sand- 

 pipers, jacanas, all of which nestle on the ground, usually 

 near the shore of the sea or lakes we judge them to be 

 exposed to about the average of dangers, since their nest 

 complement is from four to six. The northern, tundra- 

 loving cranes need raise few young, and hatch only two 

 eggs; but when we come to the water-birds the rails, 

 gallinules, ducks, and geese we find an extensive group 



