294 



BIRDS 



lay their eggs in otlier bii'ds' nests, and allow the young to 

 be fed and reared by foster parents. 



A kind of swift, found in tlie Polynesian Islands, builds 

 Hs nests in caves, and constructs theiu of a mucous secretion 

 ffhich hardens into a tough gelatinous substance. These 

 so-called "edible nests" are used as food by tl.c Chinese. 



Fig. 199. — Oriole's nest. 



Many birds secrete mucus from the salivar}' glands which is 

 used to fasten the materials together of which their nests 

 are built. 



The hanging nests of our Baltimore orioles (Fig. 199) 

 and of the japim of South America are objects of very 

 great interest. The social weaver birds of South Africa 

 fjuild domelikt^ structures out of straw beneath whicli may 

 ))e twenty or thirty individual nests. Tlie female hornbill 

 of Africa, Asia, and Australia enters a hollow tree to build 



