THE YOUNG BIRD 79 



concerned. Fully adult, vigorous birds probably lay larger and more 

 heavily pigmented eggs and more of them than their younger or weaker 

 fellows. Again, the first eggs of a set, as well as those of first sets, where 

 more than one is laid, may be more strongly pigmented or larger than 

 those laid later. But whatever their cause, the cataloguing of these 

 variations constitutes no small part of the labors of the oologist, whose 

 delight in finding an unusually large set, or one containing 'runt' eggs, 

 or colored eggs which should be plain, or plain eggs which should be 

 colored, is somewhat out of proportion to the scientific value of the 

 'discovery/ 



Incubation. The period of incubation is more or less closely related 

 to the size of the egg. With the Chipping Sparrow it is twelve days, 

 but with the Ruby-throated Hummingbird fourteen; the English 

 Sparrow requires twelve or thirteen, the Robin thirteen or fourteen, 

 the Fish Hawk about twenty-eight, but the exact period has been 

 ascertained for comparatively few of our birds. 



Incubation is usually performed by the female and is sometimes 

 equally shared by the male; or the male may merely cover the eggs 

 during the female's absence; or again, as with the Ruby-throated 

 Hummingbird, he may not be seen near the nest after the eggs are 

 laid. With the Phalaropes the male alone incubates. 



The treatment of their eggs by sitting birds is a subject concern- 

 ing which we have not much information, though some birds are known 

 to turn them with their feet and others with their bills. I have seen a 

 Least Bittern calmly eat two of her five eggs which had been punc- 

 tured by a Marsh Wren, and then settle herself on the remaining three. 

 ("Bird Studies with a Camera," p. 75.) 



The disposal of the egg-shell is also a matter of interest. Most 

 birds carry it some distance from the nest before dropping it, but young 

 Flamingoes eat it! 



The Young Bird 



