294 



BIRDS 



lay their eggs in other birds' nests, and allow the young to 

 be fed and rearetl by foster par-ents. 



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

 its nests in caves, and constructs them of a mucous secretion 

 which hardens into a tough gelatinous substance. These 

 so-caUed "edible nests" are used as food by the Chinese. 



Fig. 199. — Oriole'.s nest. 



Many birds secrete mucus from the salivary 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 ai-e ol^jects of very 

 great interest. The social weaver birds of South Africa 

 build domelike structures out of straw beneath -which may 

 be twenty or thirty individual nests. The female hornbill 

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



