346 BIELD ZOOLOGY. 



neath the skin, and the unusually large air cavities in the 

 long bones of the wings and the legs ; these are hollow for 

 their entire length, being solid only at the ends where 

 they enlarge to provide for attachment of muscles. If 

 one presses the skin of a pelican in the pectoral or the 

 ventral region, there is heard a crackling sound as the air 

 is driven in and out of these enormously developed 

 pneumatic reinforcements of the respiratory system. 



The young of the order are altricial ; the eggs are very 

 few, in most species of the birds only one, plain colored 

 and coated with a chalky-white substance. North 

 America has ten species of cormorants, fotir of which 

 nest within the United States; the Florida and the 

 Mexican nesting in Florida and the Rio Grande country, 

 respectively. Of the other two, the white crested and 

 the common, the former nests in the northwest, Oregon; 

 and the latter in the marshes of Iowa, Wisconsin, and 

 some of the inland lakes. Pelicans build nests on the 

 ground or in low bushes, cormorants on rock ledges or in 

 crevices of some rocky cliff, or in bushes; frigate birds 

 in low, thick bushes by the water's edge. The nests of 

 the last are made of sea weeds, mud, small stones, sticks, 

 bark, and grasses, usually placed on the ground by the 

 water's edge or on islands. The white pelican spends its 

 winters in our southern states along the Atlantic, in the 

 Gulf states, and in Mexico. 



The cormorants are social birds, often nesting in 

 immense colonies, their nestirtg grounds are exceedingly 

 offensive, owing to their uncleanly habits in using excre- 

 mentitious matter for a partial covering for the eggs. 

 The decomposition of this matter serves to raise the nest 

 temperature sufficiently high for incubation while the 

 bird is away from home. 



