WATER BIRDS. 209 



the glands, but I have no hesitation in coming to a con- 

 clusion which, to my mind, is perfectly satisfactory, and 

 that is, that they are simply excretory. In the course 

 of my examination of various species, I found that not 

 merely were the webs of the feathers of aquatic birds 

 oily, but that the shafts and quills were equally so. 

 The chief food of most pelagic species is of an oily 

 nature ; and their stomachs are filled with oil to such an 

 extent that, as is well known, the body of a fulmar petrel, 

 with a wick of cotton drawn through it, is the common 

 lamp of the inhabitants of St. Kilda. I have also often 

 seen the Cape pigeon (Daption Capensis) vomit nearly 

 a tablespoonful of clear oil when captured. It is evident 

 that in these and similar species which seek their food 

 on the water, no outward application of oil to their 

 feathers is necessary, for both skin, flesh, and feathers 

 are thoroughly impregnated with it. 



In support of my view we find, as I said before, that 

 those birds whose food is obtained from the water, and 

 whose flesh and skin are more or less oily, are fur- 

 nished with two glands, in some species of large size ; 

 whilst land birds, whose flesh is generally free from oili- 

 ness, have only one gland ; and in some of these, as in 

 the black grouse for instance, it is very small, though 

 singularly enough, the red grouse and ptarmigan have 

 each two glands, but very small. An apparent excep* 

 tion exists in the white-tailed sea eagle, which has, like 

 the rest of the rapacious birds, but one gland ; but 

 though it feeds on fish, which it captures in the water, 

 lambs, hares, and other animals also enter largely into 

 its diet. But there is another more remarkable exception 

 to this arrangement, and one totally incompatible with 

 the popular idea, and that is the group of the penguins. 



P 



