Plumages of the Male Crossbill. (569 



speaking, the males are red and tlie females yellow ; we also 

 find the same thing in some jNlinivets, while in the Scarlet 

 Tanager and Orchard Oriole the red of the male in summer 

 is replaced hy yellow in winter and iu females at all times of 

 the year. Then, again, we find a yellow-headed variety, as 

 Mr. Seth Smith informs me, of the Red-headed Gouldiau 

 Finch (Poephila miraJnlis) occurring in nature, and I have 

 seen red feathers occurring among the bright yellow feathers 

 of the Green Woodpecker. ]Many other such instances of 

 correlation between red and yellow could doubtless be given. 



It has been suggested by vonTschusi that this yellow dress 

 of the Crossbill is atavistic, a reversion to an ancestral 

 plumage, — a theory which it is well-nigh impossible to prove, 

 and which appears to me little better than admitting one's 

 ignorance of the explanation of the phenomenon. Seeing how 

 very much more common this yellow dress is in males of the 

 first year than in older birds, it is tempting to suggest that 

 this plumage is the normal one for first-year birds, and is 

 being gradually skipped over for the commoner red plumage; 

 in slight support of this it may be remarked that the yellow 

 plumage iu the Pine Grosbeak males is the usual plumage 

 of the first year, though red birds do also occur. However 

 feasible this sounds, it will not explain the as-sumption of the 

 yellow plumage in part or iu whole by birds , of more than 

 one year. 



From the lesson of the behaviour of birds in captivitv 

 towards coloration, it does seem probable that food has an 

 influence on coloration and that some particular food is 

 necessary to produce the red eolour. Is it possible that at 

 the period of moult, in any given area inhabited by Cross- 

 bills, there is not enough of this food to go round, and 

 that as a consequence some birds do not get enough red- 

 producing food and therefore moult into a yellow-green 

 di-ess? This is of course only a theory, and proof for or 

 against it, is, I am afraid, very difficult to obtain. 



