752 Birds. 



more Essays on this, or any kindred topic, I shall merit and obtain 

 the full approbation of its readers, without one single exception. 

 That I should not manfully state my own opinions, and deal plainly 

 with his arguments, Mr. Waterton would be the last to wish ; but if 

 I write as I feel, I shall do so not less courteously than plainly. 



I shall commence by admitting, what Mr. Waterton has shown, that 

 I did not carry my observations far enough to render them conclusive. 

 I confess, not that I " ought to have seen the expressed matter," for 

 it would have been within the bill, not on its " sides ;" but, that I 

 ought to have noticed whether the tuft of down on the extremity of 

 the nipple was or was not moistened by the matter. This I omitted 

 to do ; thereby betraying a want of sagacity which I have abundant 

 cause to regret. 



This tuft is much longer in some birds than in others ; and in very 

 small birds, if it exist at all, it is not discernable by the naked eye. 

 I have this day (Sept. 13), examined the state of the oil-gland in 

 four recently killed birds : in two partridges the tuft, though small, 

 was sufficiently large to show that it was saturated with an unctuous 

 matter : in a knot, shot by myself, in the act of preening its feathers, 

 the tuft was nearly half an inch long ; and when examined, three 

 hours after death, was completely saturated ; while the surrounding 

 feathers were unaffected. The fourth bird was the little willow- 

 warbler, which had been very recently killed : it had no tuft ; but very 

 slight pressure, scarcely more than the mere movement of the nipple 

 with a small instrument, sufficed to produce matter from the orifice. 

 Now I cannot help feeling that here is evidence enough, not only of 

 the existence of an unctuous fluid, and of an orifice by which it may 

 be expressed — this, I think, Mr. Waterton does not question — but 

 that this matter does readily flow from the orifice, and moisten the 

 tuft on the apex of the nipple : and may I not fairly ask Mr. Water- 

 ton how the kestrel could take the nipple between its mandibles in the 

 manner I witnessed, and not express matter therefrom ? 



I think the movements of the bird were too deliberate, and the act 

 too frequently repeated, to admit of the interpretation Mr. Waterton 

 would give. The cessation in the process of preening ; then the 

 erection of the feathers surrounding the gland by the muscular action 

 of the skin, exposing the nipple to view, as well as to ready access 

 by the bill; then again the deliberate seizure of the nipple, and the 

 three or four nibbles, for so I may call them, though differing from 

 the rapid movement of the mandibles when the bird clears itself of 

 parasites, followed by immediate application to the feathers, too 



