278 A HISTORY OF BIRDS 



selection, whereby the bird might, by its more sombre hues, 

 escape these dangers until the power of flight returned again. 



A closer examination of the facts, however, serves to show 

 that this interpretation must go, or must at least be largely modi- 

 fied. It would seem that this " eclipse " dress, worn for some few 

 weeks only, answers really to the " winter " plumage or post- 

 nuptial dress of the Limicolae, for example. In the two groups 

 the period of the two liveries is reversed then. That is to say, 

 the bright colours of the one are donned for a very few weeks 

 only, and discarded for a more sombre garb, worn during the 

 rest of the year ; while in the other they are worn during the 

 greater part of the year, so that it is the dull garb which is 

 evanescent. In short, the differences between these two groups 

 are really two phases, two links in the chain of the evolution 

 from a dull to a brightly coloured plumage, the latter tending 

 more and more towards persistence until it becomes permanent, 

 the older, dull plumage, appearing only in the young, and 

 finally becoming eliminated from the life-history altogether, as 

 in the Parrots and Kingfishers, for example. Even among 

 those groups which have acquired a permanently brightly 

 coloured plumage remains of the older, dull plumage still 

 persists, appearing for a season during the annual moult. Thus 

 in Gallus the neck-hackles are for a time discarded, and simi- 

 larly in the Blackcock, during the late summer, the head and 

 neck puts on a dull brown covering, to be replaced immediately 

 by the normal colours. That the head and neck should be the 

 last to put off the final relics of the older, dull-coloured plumage 

 is interesting, since here too the last traces of the down plumage 

 remain while the rest of the body is fully feathered. That the 

 " eclipse " plumage of the Duck is protective is highly probable ; 

 and but for the need for some such protection it is also probable 

 it would have been eliminated altogether. 



Much light will doubtless be thrown on the problems of this 

 evolution of plumage when more material has been collected 

 on the subject of moulting among birds. At present our 

 knowledge of this subject is of the most meagre description. 



That birds from time to time renew their plumage by the 

 process known as moulting is matter of common knowledge ; 

 and in this periodic change of raiment they agree with the 

 amphibia, reptiles and mammals. But it is not so generally 



