CHAPTER XXI 



THE FOOD OF ANIMALS— OMNIVOROUS BIRDS AND 

 PROTOCHORDATES 



Some of the more interesting adaptations which Birds exhibit 

 to a purely or mainly animal or vegetable diet have been described 

 in preceding chapters. A large number of species are omnivorous 

 to a greater or less extent, but it would be dull and profitless to 

 do more than mention a few types, as such a procedure could be 

 little more than a list of birds with their appropriate food. It 

 may be noted that in cases where the structure presents no 

 marked peculiarities as regards the digestive arrangements, and 

 especially when the beak is a fairly-strong cone of average length, 

 a miscellaneous bill of fare is apt to be found, though no hard- 

 and-fast rule can be drawn. In such Birds, too, it commonly 

 happens that the food varies at different times according to what 

 the season has to offer, and a fact previously mentioned may also 

 be borne in mind, i.e. that the food of the nestling may differ 

 from that of the adult. The stock example of this last point is 

 the common House- Sparrow, which, though vegetarian itself to all 

 intents and purposes, feeds its young on worms, caterpillars, and 

 the like. 



CROWS (CoRViD^) 



As might be anticipated, some of the most careful observations 

 regarding the food of birds have been made with reference to 

 species which affect the interests of farmers and other cultivators. 

 Such, for instance, are the Raven, Carrion Crow, Rook (fig. 456), 

 and Jackdaw (species of Corvus), well-known members of the 

 Crow Family, now usually placed at the head of the large group 

 of passerine or perching birds, commonly considered to be the 

 highest group of the enormous assemblage of flying-birds (Cari- 

 natse), to which all living forms, except Ostriches, &c., belong. 

 Professor Ritzema Bos (in Animal Foes and Friends) thus speaks 



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