1920.] Shtdy of Nestling Birds. 861 



Accentors, Tree-creepers, Robins, and in the Nightingale 

 and Stonechat. 



On the other hand, it will be noticed that the young of 

 altricial species nesting in more open situations, either on 

 the level ground or among the looser vegetation of shrubs 

 and low trees, are generally covered with down of a very 

 much lighter shade. A moment's reflection will, I think, 

 explain the reason for this. In sucli positions, it is obviously 

 an advantage to neutralize, rather than intensify, the depth 

 of shadow in the nest-cup. 



With a few exceptions among arboreal species, the down 

 varies in colour from smoke- or drab-grey in birds that 

 select moderately low sites (i. e., Chaffinch, Greenfinch, 

 Linnet. Blackbird, Song-Thrush, etc.), to white or whitish 

 in those that nest in higher and still lighter positions 

 (Hawfinch, Goldfinch, Golden Oriole, Mistle-Thrush, etc.*). 

 It is also significant to note that in these latter species tlie 

 down is generally more profuse — compare, for instance, the 

 Mistle-Tlirush with the Song-Thrush or Blackbird, or 

 the Hawfinch with the Linnet. 



With giound-nesting birds (i.e., Field-Wagtails and Larks), 

 that build their nurseries on a level surface, and therefore 

 more or less open to the sky, the down is generally distinctly 

 more sandy in hue. This colour assimilates equally well 

 with the sun-dried ground of sterile districts or the parched 

 stems that are found near the roots of all kinds of grassy 

 vegetation. \\\ the case of some of the Larks, the assimila- 

 tion IS not due to colour alone, but is considerably ;issisted 

 by a special modification of the down-feather. A good 

 example of this can be found in the Common Skylark 

 (Alauda arvensis). Upon comj)aring the nestling-down of 

 this species with that of most other Passerine birds, it will 

 be noticed that it appears very coarse in texture. This is 



* An apparent exception to this rule occurs in tlie Crossbiil. Accord- 

 ing- to Ticf»liurt<t, the nestling-down of this bird is very dark grey. 

 Although nesting liigh, I believe it usually builds iu rather dense 

 branches of dark-leaved conifers, in which ease the downy covering 

 niiiy still be regarded as ]irocryptic. 



