W. p. PYCRAFT : NESTLING BIRDS. 167 



Thoug-h not g-enerally realized, it is a fact that the 

 relative amount of down which Passerine birds develop 

 varies g-reatly, and its distribution also varies. The 

 study of the nestling-down of other types is more 

 complex and difficult : yet it will well repay a careful 

 study. Of this I am convinced, because, in conjunction 

 with my friend, Mr. J. L. Bonhote, I have already gone 

 some way into this matter. Together, we hope shortly 

 to lay before the readers of British Birds some of our 

 conclusions. 



Such, then, in bare, brief outline, are some of the 

 main problems which await further investigation. On 

 one or two points photography could be made to render 

 good service. Tlius, somewhat enlarged photographs are 

 needed of nestlings such as have striped or mottled down, 

 inasmuch as these patterns, in skins, are always more or 

 less interfered with. Such photographs should show both 

 the living and dead bird, the latter giving a full view of 

 the upper surface ; while photographs of nestlings of 

 downy Passerine types would be invaluable, since skins at 

 this stage are always more or less unsatisfactory, and 

 collections in spirits can only be housed by museums. But 

 these photographs, to be of any service, must be superbly 

 good, very sharply focussed, and slightly enlarged. The 

 method whicli we propose should be adopted, by way of 

 illustrating the developmental stages of the down and 

 feather plumage in Passerine birds, is shown in the plate 

 which accompanies this article. These most admirable 

 pictures we owe to the kindness and skill of Miss E. L. 

 Turner, and in justice to her we should remark that some 

 of the more delicate details of the down in the younger 

 nestlings have inevitably been lost in reproduction. 



A large series of nestlings of British birds dealt with 

 after this fashion would prove of the highest value. By 

 the way, I would mention here that, by a slip, the colour 

 of the mouth of the nestling Bearded Tit was described in 

 my last article as yellow instead of pinlc, spotted with 

 white. 



