NATURAL HISTORY STUDIES 



in the swan, and over seven weeks in the condor, 

 and the risks of discovery are often great. The 

 nest means safety. Secondly, the eggs and the 

 young take on the temperature of the surrounding 

 world, and when they cool below a point, which 

 differs for different kinds, they cease to develop 

 and soon die. -The nest often economizes the animal 

 heat of the brooding bird, so that there is little waste. 

 It is also evident that the nest is convenient for 

 feeding purposes, and as a temporary prison for 

 the nestlings, so that they are less likely to make 

 rash excursions. Sometimes the nest serves for a 

 certain amount of home-education. Furthermore, 

 the nest is often a comfortable and secure resting- 

 place for the parent birds. 



A Series of Nests 



Let us survey the series of nests from the 

 simplest to the most complex. We naturally begin 

 with those birds in which the nest-building is 

 " scamped " or shirked. 



The tern makes no more than a mere scraping 

 on the gravelly sand. It is the same with divers, 

 thick-knees, sand-grouse, and many other birds. 

 In the case of guillemots and razorbills, the egg is 

 laid on a bare ledge of rock, and the top -like shape 

 is to some extent a safeguard against being blown 

 over or knocked over. 



Many of the gulls, sandpipers and plovers simply 

 lay their eggs in shallow hollows in the ground, 

 adding a breastwork of stems and leaves as brooding 

 proceeds. The ducks are mostly about the same 



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