Page:Birdlifeguide00chap.djvu/23



CHAPTER I.

THE BIRD : ITS PLACE IN NATURE AND RELATION TO MAN.

 The Bird's Place in Nature. —About thirteen thousand species of birds are known to science. The structure of many of these has been carefully studied, and all have been classified, at least provisionally. Taken as a whole, the class Aves, in which all birds are placed, is more clearly defined than any other group of the higher animals. That is, the most unlike birds are more closely allied than are the extremes among mam&shy;mals, fishes, or reptiles, and all living birds possess the distinctive characters of their class.

When compared with other animals, birds are found to occupy second place in the scale of life. They stand between mammals and reptiles, and are more closely re&shy;lated to the latter than to the former. In fact, certain extinct birds so clearly connect living birds with rep- tiles, that these two classes are sometimes placed in one group—the Sauropsida. 3