THE VERTEBRATES 433 



rapid oxidation of birds their temperature is higher than 

 that of mammals, some birds reaching 110 F., which would 

 be fatal in a mammal. 



357. Classification of Birds. No classification of birds 

 yet prepared has been generally accepted, and no two books 

 agree. The difficulty arises from the fact that the 12,000 

 species of birds are remarkably similar except in details of 

 structure. It is not possible in limited time to describe 

 the groups of birds, and for general purposes it is most con- 

 venient to name groups according to some of their well- 

 known representatives, as in 1 to 16 below. For each of 

 these groups there is a scientific name, for which see special 

 books on birds. 



Groups of Birds 



1. Ostrich group ostriches, emu, cassowaries, kiwi (Apteryx), 



moas. All wingless or with greatly reduced wings. 



2. Loon group loons, divers, grebes. 



3. Gull group gulls,, terns, petrels, albatross. 



4. Pelican group pelicans, cormorants. 



5. Duck group ducks, geese, swans. 



6. Heron group herons, bitterns, storks, flamingos, spoon-bill. 



7. Rail group rails, coots. 



8. Snipe group snipes^ plovers, woodcock, "killdeer." 



9. Pheasant group pheasants, grouse, quails, chickens, turkeys. 



10. Pigeon group - pigeons, doves. 



11. Eagle group eagles, hawks, vultures, falcons. 



12. Owls. 



13. Cuckoo group cuckoos, kingfishers. 



14. Woodpecker group woodpeckers, flickers. 



15. Humming birds. 



16. Perching or song-birds, 6000 species sparrows, warblers, 



crows, jays, fly-catchers, finches, robins, thrushes, bluebirds, 

 etc. Includes all the most interesting song-birds. 



A popular classification arranges birds according to their 

 habits as wading birds, birds of prey, swimming birds, climb- 

 ing birds, and perching birds. This is very convenient for 

 most people, for they are chiefly interested in how birds live 



2F 



