1142 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



started before July 22, As it takes some 70 days after egg-laying to 

 bring young through the postju venal molt, such a late brood could 

 hardly be ready to migrate by September 29, the latest record for the 

 species' occurrence there. 



Song is the tree sparrow's chief asset in courtship display, for the 

 species is plain colored and the sexes are alike. In courting either 

 sex may be the aggressor, pursuing the other and flaunting its humble 

 beauties. Of one pair observed for some time and finally collected, 

 the pursued bird proved to be the male. One nest-building female 

 approaching her nest with a ptarmigan feather was filled with a 

 sudden excitement when her mate came to sing nearby. She dropped 

 the feather, hopped to a twig about a foot from the ground, spread 

 and fluttered her wings, and uttered an alluring ''wehy-wehy-wehy- 

 wehy.'' The male sang on indifferently, and she picked up her feather 

 and went onto the nest. 



In another case the female fed quietly on the ground while her 

 suitor, sitting on the bush above her, uttered a rapid series of stacatto 

 chips, puffed his plumage, spread his wings, and then darted to the 

 ground with much fluttering. In acknowledgment she preened 

 daintily, fluttered her wings with neck much extended, and miu-mm*ed 

 the soft "wehy" notes which brought him to her. Fluttering over 

 her for an instant, he copulated and darted back to his perch. He 

 repeated the procedure several times in the next two minutes. There 

 was no singing at this time. Sometimes copulation took place without 

 display of any kind, the male simply flying to his mate while she was 

 feeding or at the nest. The nest I pair were seen to copulate at the 

 nest on three occasions, once during its building, twice within haK an 

 hour the day before the la3Ting of the second egg. 



The extent of the tree sparrow's summer territory proved to be 

 considerably smaUer than the winter feeding range, as anticipated. 

 Two nesting areas were studied in detail: a stretch of open tundra 

 bordered on one side by a small patch of brush, near which was a 

 single nest (nest I) : and a tangled thicket of low wUlows and birches, 

 extending some 300 by 800 feet along the river flats, mthin whose 

 confines dwelt four families in 1933 (nests III-VI) and three in 1934 

 (nests C, D, E). 



Though I marked no adults the first season for fear of upsetting 

 their natural behavior patterns, I could tell the males apart by their 

 song patterns, and the females by watching them as they left the nest. 

 In 1934 I decorated a few adults with gay chicken feathers to corrobo- 

 rate the first year's observations. Young birds were banded, but the 

 tailless, soft juvenal plumage would not hold additional feathers 

 (Heydweiller, 1935). 



