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THE BIRDS 



place. The eider down duck lines her nest with the fluffy down feathers 

 plucked from her own body, which we remove to stuff our best down 

 quilts. There is a bird, the Selangane swift, that lives in Malay and 

 surrounding Pacific islands that lines its nest with a gelatinous material 

 secreted from its throat. These nests are collected and sold to the Chi- 

 nese to make bird's nest soup. The nests are built in rather inaccessible 





t # 



Photo by Winchester 



Fig. 27.4. Young barn owl. Most young birds are quite unattractive when young as 



illustrated by this specimen. This is in contrast to many higher forms of animal life 



where the young are more attractive than the adults. 



caves along the seacoast, and their collection is somewhat hazardous. 

 The best grade nests bring from ten to fifteen dollars per pound. 



The number of eggs laid by birds varies from one to twenty or more. 

 The eggs are similar in structure to the reptile eggs, although the shell 

 is calcified and brittle. Also, they must be incubated, for the birds are 

 warm-blooded animals and a tiny embryo cannot generate enough heat 

 through metabolism to keep its body temperature normal. We some- 

 times have to place human babies in incubators when they are born pre- 

 maturely and are not large enough and well-developed enough to pro- 

 duce the heat needed to maintain normal body temperature. The female 



