BIRDS 



287 



the relative importance, numerically, of these various cate- 

 gories among the birds which may be found in a certain region, 

 and thus form its bird-fauna, we may illustrate by reference 

 to a definite region. Of the 351 species of birds which have 

 been found in the state of Kansas (a region without distinct 

 natural boundaries, and fairly representative of any Mississippi 

 valley region of similar extent), 51 are all-year residents, 125 

 are summer residents, 36 are winter residents, 104 are migrants, 

 and 35 are rare visitants. 



\ 



FIG. 131. Nest of song sparrow (Melospiza cinercd). 

 (Photograph by J. H. Paine) 



The all-year residents and the summer residents, comprising 

 about one-half of the species to be found in a locality, are the 

 only ones which breed there, and which thus present oppor- 

 tunity for observations on their nest-building habits and care 

 of the young. Numerous suggestive questions present them- 

 selves in connection with breeding. Why is it that some 

 species nest early and some late? Can the character of the 

 food of the young have anything to do with this? If so, what? 

 Does the condition of the particular trees, bushes or other 

 favorite sites for nests help determine the nesting time? Why 



