THE LIFE-HISTORY OF BIRDS 271 



The Passerine birds present us with the other extreme of 

 nesth'ng- pkimage, in that the down feathers are here but feebly 

 developed, or are absolutely wanting, as in the Sparrow and 

 Crow tribe. Young Larks and Wagtails have more down than 

 Thrushes, but this is never developed save in certain restricted 

 areas. That is to say, instead of every contour feather being 

 preceded by a down feather, as in the young of nidifugous 

 birds, only a few have these fore-runners. Thus a row of 

 down feathers occurs over each eye and a few around the back of 

 the head, while a row of downy tufts runs down the scapular 

 tract, and a similar row along the spinal and femoral tracts. 

 But the under-surface is always bare. That this condition has 

 been derived from a more complete covering is shown by the 

 fact that the Lyre-birds alone among the Passeres have a com- 

 plete downy covering, and these birds represent, probably, the 

 most primitive members of the group. Thus we have, among 

 the Passeres, every gradation from a thick, woolly covering to 

 absolute nakedness, and the specialisation in this matter runs 

 hand in hand with specialisation in other particulars. 



The passage from the downy to the feathered stage is often 

 very gradual, as may be seen, for example, in the young of 

 Game-birds, where the head and neck, the middle of the breast 

 and the lower part of the back retain their down until after the 

 rest of the body is clothed with typical feathers. 



The first plumage of true feathers is instructive. Where 

 the sexes of the adults differ in coloration the young resemble 

 the female, though this resemblance may be only very approxi- 

 mate. On the other hand, as in the Koel {Eudyiiaiiiis orioitalis) 

 — a Cuckoo — and in a Starling {Ajnydrus blytJii) the young of 

 both sexes wear the plumage of the male, the females later 

 assuming the dress characteristic of their sex. The adult female, 

 in the case of the Koel, it may be remarked, is brown, the male 

 black ; while in the Starling the female is glossy black with 

 a pure grey head and neck, the male entirely black. So that, 

 while in the case of the Cuckoo the female apparently retains 

 an ancestral livery, in the Starling the female would seem to 

 have assumed a more highly specialised, resplendent livery, 

 independently of the male, unless indeed this female dress re- 

 presents an earlier male dress. Where the adults of both sexes 

 are similarly coloured the young either differ from both parents, 



