1368 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



throated sparrow, the higher rate of singing of white-striped males 

 attracts more females of either type. Thus white-striped males would 

 have a greater choice of females from which to select their mates. 

 By driving off the singing white-striped females, they monopolize the 

 available tan-striped females and leave the white-striped females to 

 mate with the tan-striped males. 



As already mentioned (see also Voice), the trill of the female appears 

 to be a precopulatory note which incites the male. When trilling, 

 the female crouches on the branch, holds her tail level with or slightly 

 above the line of the back, and flutters her wings. The male approaches 

 with a relatively slow fluttering flight. Upon his approach, the 

 female increases the intensity of trilling and wing-fluttering. The male 

 mounts the female, and copulation occurs. Both partners preen for a 

 few seconds following copulation. 



Nesting.- — Only the female white-throated sparrow builds the nest. 

 In 1959 and 1960 in Algonquin Park, Ontario, eight banded female 

 white-throats were observed carrying nesting material. In both years 

 several male birds were under close observation, but none was ever 

 seen carrying nesting material. As the female builds the nest with- 

 out help from the male, she probably also selects the nest site. 



Little is known about the process of nest building. During the 

 Algonquin Park studies, it was estimated that nest-site selection and 

 nest building took place between May 14 and May 22. Birds were 

 seen carrying nesting materials only in the morning activity periods. 

 The area over which the birds seek nesting material, the number of 

 trips made to and from the nest, and the total time involved in nest 

 building are not known. 



If the nest suffers predation, or if the bird renests in the same gen- 

 eral area in subsequent years, it builds a new nest a considerable 

 distance from the first. Of the six renests noted in Algonquin Park, 

 each was more than 100 feet from the first. 



Lowther analyzed 39 nests for nesting materials. Each nest was 

 divided into the outer portion and the inner fining, and each portion 

 was analyzed separately. The other portions were made of coarse 

 grasses in 36 nests, wood chips in 30 nests, twigs in 14 nests, pine 

 needles in 10 nests, roots in 7 nests, and small quantities of deer hah-, 

 moss, and fine grasses in 4 nests. The linings were composed of fine 

 grasses and rootlets in 38 nests, deer hair in 36 nests, pine needles in 8 

 nests, and small quantities of wood chips, twigs, roots, and mosses 

 in 2 nests. 



With few exceptions the nest is built on the ground at the edge of a 

 clearing, and is usually well concealed by the ground vegetation. 

 There are seven records of nests built off the ground. Macoun (1904) 

 reported four of these — in the roots of an upturned stump, in a small 



