How to Study Birds 



91 



could not fashion a Woodpecker's dwelling; but a momentary comparison 

 of the widely different kinds of nests built by Swallows and Swifts 

 (which, so far as nesting tools are concerned, may be classed with Swal- 

 lows) readily shows how little the structure of the bird has to do with 

 nest architecture. 



By far the most important factor governing the character of a bird's 

 nest is the condition of its young at birth. Indeed, in considering this 



SIMPLE NEST OF KILLDEER, A PR^COCIAL BIRD 



(Meridian, N. Y.. June 7, 1898) 



question we are brought very near to an attempt to determine the origin 

 of birds' nests. 



In a rough classification we may place birds in two groups: first, 

 those whose young leave the nest the day they are hatched; second, 

 those whose young are reared in the nest. Birds of the first class are 

 termed praecocial; those of the second, altricial. Compare the newly 

 hatched young of a Grouse with those of a Robin, and we have two 

 admirable examples of praecocialism and altricialism. 



