voL.xiv] BlUTISH HAWKS NESTLING-DOWNS. 155 



white and growing very sparsely here and there amongst the 

 pre-pennae or doian (a). 



Down (c). — When the nesthng is about ten days old it 

 begins to be covered very thickly with a long and coarse 

 (woolly in some species) down, which is usually of a grey or 

 brownish-grey colour. When fully grown it almost entirely 

 conceals the down (a) and it replaces the short tufts of doivit (b) 

 which can be seen clinging to its tips here and there, but it 

 also grows in many parts where there is no previous down. 

 This down is shed when the first true feathers are nearh^ 

 grown. The under-down (" plumul?e ") of the feathered 

 bird grows about the same time that dozen (c) is shed and is 

 always of a different structure and often of a different colour. 



I have found these three downs in nestlings of such different 

 genera as Falco, Aquila, Buteo, Circus, Accipiter, Milvns, 

 Pandion, but of the other genera I have not been able to 

 examine nestlings in a stage to make certain that down (b) 

 is present, although all seem to have (a) and (b). 



