CHAPTER XXIV 

 BIRDS 



The birds, class Aves, the most familiar and attractive of 

 wild animals, have been the object of so much attention and 

 study by professional naturalists, amateur nature students and 

 just nature lovers, that their classification, life history and 

 habits are better known than are those of any other animal 

 group. 



About i2,ooo l different species of birds are known from all 

 the world, of which about 800 occur in North America. In 

 any single favorable locality in this country one can get ac- 

 quainted with from 100 to 200 species, counting in those 

 kinds that pass in the fall and spring migrations as well 

 as those that nest in the locality. The number of kinds 

 that may be called "all-year residents," that is, which 

 remain in the same region through the whole year, is, however, 

 very small, averaging usually about one-seventh of the total 

 number that may be seen in the region during the course of a 

 year. This limited number of kinds of birds in any one 

 locality, together with the bright colors and characteristic 

 manners which make their identification easy, the interest 

 of their songs and flight and their feeding, nesting and general 

 domestic habits, make birds excellent subjects for personal 

 field studies by students. And if the food habits are studied 

 from an economic point of view, valuable practical informa- 

 tion can be obtained during the study. 



General Structure. The general body form and external 

 appearance of a bird are too familiar to need description. 

 The covering of feathers, the modification of the fore limbs 



1 The British Museum Catalogue lists nearly 19,000 species but it 

 recognizes as full species about 7000 forms considered by most ornitholo- 

 gists to be merely varieties or sub-species. 



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