3974 Birds. 



have afterwards assumed, either wholly or in part, a white or other- 

 wise unwonted dress, there is much variety of opinion ; and, indeed, 

 much mystery seems to involve this change of plumage. The effect 

 is frequently seen in different species, but the causes producing that 

 effect in many cases lie hidden, although I think there can be little 

 doubt that these changes spring from a variety of causes, not one hav- 

 ing yet been started which will apply to any considerable number of 

 the cases I have investigated. Amongst the many causes proposed 

 by different naturalists for this occasional and unnatural change of 

 colour, Montagu and Bewick unite in thinking that confinement is the 

 chief; and it seems consonant with reason that this may sometimes 

 be the case, as a caged bird necessarily loses all his natural habits, 

 and is constrained to use only the prison diet, whatever that may 

 chance to be. Again, in the case of a bullfinch which gradually be- 

 came coal-black, Gilbert White attributed it to the hemp-seed upon 

 which he was fed, concluding his account of it with this reflection, — 

 " such influence has food on the colour of animals ; " a conclusion, 

 the universal truth of which I must lake leave to dispute: for certainly 

 this is not the invariable effect of that seed, inasmuch as birds fed en- 

 tirely on hemp have retained their wonted colour, while others have 

 become completely black, when fed upon canary-seed alone. A third 

 cause, proposed by others in some cases, has been fright ; and I have 

 already stated my firm persuasion that a variation in colour has en- 

 sued upon great and sudden terror. In this I have been supported 

 by many naturalists, and by no more conclusive proof (though it es- 

 caped my notice at the time) than the account related by Mr. Fennell 

 (Zool. 565). 



" Zoologists certant, et adhuc sub judioe lis est." 



But although we may prove that one bird is terrified until his hair 

 turns white, and another eats hemp-seed till he's black in the face, 

 and another is imprisoned till he's purple with rage or white with pas- 

 sion, yet we cannot imagine that any of these are the usual causes of 

 the variations in colour which so frequently come under our notice ; 

 especially as the greater part of these instances relate to birds always 

 at liberty, with which sudden fright can have little, and hemp-seed 

 and confinement nothing at all to do. And even of birds kept in 

 cages, numbers are daily frightened and fed with hemp-seed, and yet 

 retain their usual dress ; the variation in colour ensuing from cither 

 of these causes is the exception, not the rule. We must then look 



