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NOTES ON THE NESTLING-DOWNS OF THE 

 BRITISH HAWKS. 



BY 



H. F. WITHERBY. 



In a v'ery interesting paper entitled " A Contribution to the 

 Study of Nestling Birds " in the October number of the 

 Ibis, Mr. Collingwood Ingram states (p. 872) that " in the 

 young of raptorial birds the nestlings are hatched more or 

 less evenly covered with down, composed apparently of both 

 pre-penn?e and pre-plumulae," and that subsequently there 

 is a new growth of down, which Mr. Ingram evidently con- 

 siders to be plumulae. Plumules form the under-down of 

 the adult bird. 



I have recently been working out for the Practical Handbook 

 the plumages of the British Accipitres, and while I can confirm 

 Mr. Ingram's statement that the nestling has three different 

 downs, I cannot agree that the last one grown consists of 

 " plumulae," i.e., the under-down of the feathered stage. 

 This third down, which I have labelled (c) in the sequence 

 set forth below, is peculiar to the nestling stage just as are 

 the other two. It is often of a different colour from the 

 under-down afterwards grown in the feathered bird and always 

 of a much coarser and less silky structure, and usually much 

 more plentiful. In no case have I found that it is succeeded 

 by the under-down in feathered birds. It is shed when the 

 feathers of the juvenile (still in the nest or just out of the 

 nest) are nearly full grown. The under-down of the feathered 

 juvenile grows at about the same time as this down is shed, 

 but so far as I have been able to discover it is quite 

 independent. 



The nestling-downs of the British Accipitres, so far as the 

 material which has been available for examination goes, may 

 be thus described : — 



Down (a). — When first hatched the nestling is covered with 

 a fairly short down (in some such as Kites, long and hair-like 

 on the crown). This down is not very thick, and the skin is 

 usually rather bare on the sides of the neck and sides of the 

 belly. It is usually white or creamy, and is composed of 

 pre-pennse, that is to say, it is immediately succeeded by the 

 first true feathers (of the juvenile) which push it out and to 

 the tips of which it clings. 



Down (b). — This is composed of very short tufts usually 



