68 THE STORY OF THE BIRDS 



assume a downy covering, whilst in the Tropic 

 Birds and Frigate Birds they are hatched with 

 a coat of down. Most of these birds are com- 

 paratively silent ; but the Gannets are perhaps 

 the noisiest at their breeding-places. The nests 

 are usually made upon the ground, or in trees 

 or on cliffs, the birds generally breeding in large 

 societies, but the Tropic Birds do not make any 

 provision for their eggs. The Tropic Birds, 

 Gannets, Pelicans, and Frigate Birds lay one egg 

 only for a sitting, which is mostly white and 

 chalky, but spotted with brown in the Tropic 

 Birds ; the Cormorants and Darters lay several 

 eggs for each sitting. Fish is the principal food 

 of the birds in this order. 



As it is impossible to indicate or express 

 the relationships of the different groups one to 

 another in a linear series or arrangement, it 

 is quite immaterial in what sequence we deal 

 with the various orders, so we may now next 

 glance at the Anseriformes. This is one of the 

 most self-contained and natural of the avine 

 groups, becoming absolutely homogeneous if 

 we restrict it to the Swans, Geese, Ducks, and 

 Mergansers, but in it must also be included 

 the Screamers and Flamingoes. Both these 

 latter must be regarded as very aberrant forms, 



