124 THE UNIVERSITY OF THE STATE OF NEW YORK 



on the nesting grounds. Some birds do not sing until after the 

 arrival of the females, but with most species the males are sing- 

 ing when the females arrive. By song and display of plumage, 

 the males try to entice the females to settle in the chosen area 

 and fierce combats often ensue between rival males. 



a Song 



Swamp sparrow singing Nu SpS 



b Display 



White-breasted nuthatch Nu NuW9 



The photograph shows the nuthatch in display to frighten the 

 sparrow. Similar display is used during courtship to help win 

 the female and drive away other males. 



2 Time of nest building 



In New York State this varies with different species from 

 February to September. The male birds ordinarily precede the 

 females in the migration and arrive on the nesting ground from 

 a few days to a few weeks earlier. They select the general area 

 in which there seems to be plenty of food and shelter and where 

 they wish to locate for the summer and then proceed to drive 

 off other males from this area, awaiting the arrival of the females. 

 Old birds ordinarily return to the same place where they nested 

 the year before, but the young of the preceding year have to find 

 suitable places that are not already occupied. 



a Early nests 



Prairie horned lark, eggs in snow Nu LdP3 



Prairie horned lark, young in snow Nu LdP4 



Great horned owl (March) Nu OwG2 



b Late 



Goldfinch (September) Nu Go3 



3 Selection of the nesting site and nest 



a For protection 



The female ordinarily selects the nesting site and does most 

 of the nest building, while the male accompanies her and stands 

 guard ready to drive off all competitors. The choice of the nest- 

 ing site is influenced by several factors but chiefly by the need 

 for protection both from bird enemies and from the elements. 



