222 THE ANIMALS AND MAN 



spend only the winter in the locality, coming down from 

 the severer North at the beginning of winter, and going 

 back with the coming of spring; these are winter residents. 

 Some are to be found in the locality only in spring and 

 autumn, as they are migrating north and south between 

 their tropical winter quarters and their northern summer 

 or breeding home; these are migrants. And, finally, an 

 occasional representative of certain bird species, whose normal 

 range does not include the given locality at all, will appear 

 now and then, blown aside from its regular path of migra- 

 tion, or otherwise astray; these are visitants. As to the 

 relative importance, numerically, of these various categories 

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

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

 ence 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. 



The all-year residents and the summer residents, com- 

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

 are the only ones which breed there, and which thus pre- 

 sent opportunity for observations on their nest-building 

 habits and care of the yoimg. Numerous suggestive ques- 

 tions present themselves in connection with breeding in ad- 

 dition to the simpler ones already propounded in Chapter IX. 

 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, how ? Does the condition of the particular 

 trees, bushes or other favorite sites for nests help determine 

 the nesting time? Why should some birds raise but one 

 brood a year, and others two or even three? Does the fact 

 that a bird is an all-year resident or only a summer resident 

 have any influence in determining its nesting time and the 



