The Eo;o:8 of Birds 



'tDb 



437 



whose nests average a dozen eggs in each set. Explana- 

 tions are read}' for this: the birds themselves are exposed 

 to unusual peril, from weather as well as from active 

 enemies, since they mostly emigrate to the extreme North 

 and nest in the edges of marshes, where the sitting birds, 



Fig. .34/. — Xest of Laughing Citill. 



eggs, and young are all subjected to freezmgs, floods, 

 and countless marauders that depend largely upon them 

 for food during the Arctic summer, so that a heavy annual 

 recruiting must be made to repair losses. Fe^^• birds are 

 liable to so many misfortunes and mishaps as the water- 



