CHAPTER XV 



NESTLING BIRDS AND WHAT THEY TEACH 



The differences between young birds and young reptiles. Nestling birds and 

 the systematists. The clothing of nestlings. Primitive nestlings. Precocious 

 flight. Helpless nestlings. The coloration of nestling birds and its significance. 



ALTHOUGH the young of birds and reptiles agree in 

 that they are developed from an ovum provided with 

 a greater or less amount of food yolk enclosed within a 

 hard case or shell — and are not nourished by the maternal tissues 

 as in the higher Mammalia — they differ conspicuously in one 

 important particular. Among the reptiles it is no uncommon 

 occurrence for the young to emerge from the shell while still 

 within the body of the parent, or immediately after the eggs 

 are laid. With the birds the egg is invariably hatched only 

 after a prolonged period of incubation, which is performed, save 

 in some rare instances, by the brooding of one or both parents. 



The young reptile invariably comes into the world in a 

 fully developed condition. With the birds this is never the 

 case. In a very considerable number of species it is true the 

 newly hatched bird is sufficiently advanced to be able to run 

 about, and to accompany its parents in the search for food, but 

 the clothing of the body differs from that of adult life (p. 237), and 

 certain exceptions apart, the remiges or quill feathers, which 

 subserve the purposes of flight, are wanting. The young of other 

 species differ still more widely, in that they leave the shell in a 

 perfectly blind, naked and helpless condition. Between these 

 two extremes of activity and helplessness every possible gradation 

 can be met with. 



The failure of the older Ornithologists to interpret the true 

 meaning of the' varying conditions .,of the young at hatching 

 may be set down to the fact that this precocious or helpless 

 condition, as the case may be, is characteristic of large groups 

 of birds, which on other grounds seem to be, and often are, 



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