THE VERTEBRATES: BIRDS 



221 



getting acquainted with per- 

 haps fifty or sixty different 

 kinds. As birds can usually 

 be readily identified by their 

 size and shape, and the color 

 pattern of their plumage, this 

 class is especially well adapt- 

 ed for the beginning study of 

 systematic zoology, which con- 

 cerns the identification and 

 classification of species. 



There are many good "bird 

 books" to enable students to learn 

 the different kinds. For Western 

 birds Florence Merriam Bailey's 

 "Handbook of Birds of the Western 

 United States" will be the niost 

 useful. For Eastern birds , Frank 

 Chapman's "Handbook of the Birds 

 of Eastern North America" maybe 

 recommended. 



Birds and the seasons. — 



In trying to become acquaint- 

 ed with the birds of a locality 

 it must be borne in mind' that 

 the bird-fauna of any region 

 varies with the season.. Some 

 birds live in it all the year 

 through; these are called resi- 

 dents. Some spend only the 

 summer or breeding season 

 in the locality, coming up 

 from the South in spring and 

 flying back in autumn; these 

 are summer residents. Some 



Fig. 116. fsTest and eggs of the 

 ruby-throat humming-bird, Tro- 

 chilus colubris, seen from above, 

 in an apple-tree. (Photograph 

 by E. G. Tabor, permission of 

 The Macmillan Co.) 



