234 GENERAL ANALOGIES. 



swifts are the last of the land tribes which feed exclu- 

 sively upon living creatures ; and, although the food 

 is different, and requires a different form of bill, it is 

 not a little remarkable that the general structure, air, 

 and even colour of the storm-petrels, resemble those 

 of the swallow tribe ; while those of the terns have 

 more of the pratincole in them. 



GENERAL ANALOGIES OF BIRDS. 



Notwithstanding the length to which this part of 

 the subject has already extended, there are still some 

 very striking analogies of which it may be desirable 

 to take notice, the more especially that they have 

 not, so far as we are aware, been previously noticed 

 by any naturalist who has treated of the feathered 

 tribes, and also because we cannot with propriety intro- 

 duce them into the particular account of any one 

 group or genus. They are briefly as follows : 



In the first place, the flat-billed birds, which find 

 their food at the bottom of the waters, have a very 

 striking analogy to the ground -birds that feed upon 

 land. Their flesh resembles the flesh of the grazing 

 mammalia, the more exclusively that they are vege- 

 table in their feeding, as in the case of the goose. 

 The ducks, which are omnivorous, have more the 

 flavour of poultry; and those which feed chiefly upon 

 mollusca, ground worms, and the spawn of fishes, 

 partake of the racy flavour of the land "gut-birds." 

 As they become more and more feeders upon fish, 

 they acquire more and more of the rank flavour ; and 

 the auks and other species which scarcely fly at all, 

 abound very much in oil. 



It is not a little singular that it is in the two corre- 

 sponding divisions of the sea and land birds, where we 

 meet with the species which are confined to one 



