THE WORLD'S BIRDS. 131 



YOUNG. Active to some extent, but not feeding them- 

 selves, the parents disgorging into their bills, 

 which they thrust into those of the old ones. 

 They are clothed in thick uniformly-coloured down, 

 and usually differ from the adults in first plumage. 

 They fledge first on the wings. 



NEST. Various ; a burrow, or a small collection of 

 rubbish, such as twigs and pebbles. Sometimes 

 none is made at all. They always breed in 

 colonies. 



EGGS. One or two ; white, or nearly so, unmarked. 



INCUBATION. Six weeks ; those species which make 

 no nest incubate standing, keeping the egg between 

 the feet and abdomen. Both sexes sit. 



COURTSHIP. They stand face to face and rub their 

 necks together. 



FOOD. Fish and other marine animals, which they 

 swallow under water. They do not go to sea when 

 moulting, and thus cannot feed then. 



GAIT. On land an awkward waddling walk or a hop. 

 When pressed they go on all fours, using the wings 

 as legs, but usually walk and stand erect. They are 

 not plantigrade, as often stated, but walk on the 

 toes like other birds (see illustration). They are 

 most active at sea, where most of their time is 

 spent, swimming with their wings, which are 

 moved simultaneously ; they often come up to 

 breathe with a spring, like porpoises. 



DISPOSITION AND HABITS. They are very courageous, 

 and will attack man on occasion at their breeding- 

 places, using both bill and wings, as they also do 

 when fighting with each other. 



NOTE. Harsh, a bray, croak, or wail. 



ECONOMIC QUALITIES. They are useful as food when 

 nothing better is to be had, and their oil and skins 

 have been utilized. 



CAPTIVITY. They live well in this condition, requiring, 



9* 



