Retrospective Criticism, 275 



with the oily substance from the gland in question ; though I 

 have killed birds in the very act of preening themselves, and 

 have looked narrowly into their plumage as soon as I had 

 taken them up. 



The gland, in all the duck tribe which I have examined, 

 is completely enveloped in a dense tuft of inexpressibly soft 

 and downy feathers, about half an inch long ; and it is quite 

 concealed from our sight. Unless this tuft was actually 

 wanting in the Muscovy duck of which your Clitheroe cor- 

 respondent speaks (p. 1 59.), I am at a loss to conceive how 

 he could manage to get a sight of the gland through such a 

 covering. Your correspondent says, " the bird exhibited 

 the gland very distinctly." I cannot exactly understand why 

 it should be taken for granted that birds lubricate their 

 plumage, merely because they are seen to squeeze the nipple 

 of the gland with their bill, and then apply the bill to the 

 plumage. Do they equally lubricate the legs and the toes ? 

 for it is a common thing to see them bring the bill in contact 

 with these parts, while in the act of preening themselves. 

 Does not the tuft of feathers on the gland, which tuft is so 

 conspicuous in waterfowl, and in the eagle tribe, require 

 preening, and freeing from vermin? May not even nature, 

 now and then, for reasons unknown to us, call for a dis- 

 charge from this gland, which discharge the bird is enabled 

 to effect by means of its bill ; and then, after the operation, 

 may not. the bird recommence its preening? — the small 

 quantity of liquor expressed having probably descended into 

 the deep cavity of the lower mandible, and there mixed with 

 the moisture in the fauces. 



As your Clitheroe correspondent wishes that I would 

 inform him " what it is for, and what end this gland answers 

 in the economy of the feathered tribe ; " I beg to say that I 

 am in the most lamentable ignorance as to its uses. While 

 we are at the rump, I request him just to cast his eyes to the 

 other end of the bird, and tell us of what use is the cock's 

 comb in gallinaceous economy ? My old Malay fowl, Billy 

 (now dead and gone : see Wanderings, p. 240,), had nothing 

 that could be called a comb. There was merely a piece of 

 red skin, on a level with the head, and bare of feathers. 

 Two of his sons came into the world with a similar deficiency. 

 They both passed healthy, prolific, and pugnacious lives ; 

 and at last fell victims to the spit, in the common run of 

 things. Mr. Henslow's tame dove (Vol. V. p. 588.) ac- 

 tually performed a compound process, as though it were 

 gifted with the powers of reasoning. First, it lubricated the 

 plumage which was within reach of the bill ; and then, in 



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