104 BIKDS'-NESTING. 



close kin the cserulean (Dendrceca ccerulea) or Kirt- 

 land's (Dendroeca kirtlandi) warblers? Many in- 

 fluences combine, no doubt, to effect this disparity : 

 but an investigation of the comparative endurance of 

 the eggs might go far toward solving the problem. 



FLEDGLING DAYS. 



Another step toward light upon the reason for the 

 excessive rarity or abundance of any species in a 

 fauna, compared with accompanying species which 

 seem to have an equally good, or no better, chance, 

 would be to- acquire a more accurate knowledge of 

 the care of the young by the old birds in various 

 species ; the changes of temperature or other vicissi- 

 tudes which the fledglings are able to endure — among 

 the water birds and some others, they seem about 

 as tough as the adults — and the food which it is 

 needful they should have. 1 



A single example will suffice to call attention to 

 the kind of influence ,1 mean. 



Assuming as a fact that the yellowbird ( Ohrysomi- 

 tris tristis) invariably laid its first eggs at a very late 



1 So far as this point is concerned almost the first systematic observations 

 are now being carried on by Professor S. A. Forbes of Normal, Illinois ; 

 and the thanks of all ornithologists are due to him. 



