1366 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



throated sparrows occupied areas similar to ptarmigan barrens on 

 the upper plateau, but on the lower plateau they "were seen in black 

 spruce trees around borders of open areas in sphagnum bogs." In 

 Maine, the white-throat "probably [reaches] its densest population 

 at elevations on the mountains where thin soils support only a stunted 

 and openly-spaced growth of trees" (Palmer, 1949). At Churchill, 

 Manitoba, near the tree-line Falls found white-throats fairly common 

 in very local sites where the spruce forest reached its maximum density 

 and trees grew to 35 feet in height. Openings were present, however, 

 including roadsides and a railway line. In this area the more open 

 habitats with smaller trees were occupied by Harris' sparrows and 

 white-crowned sparrows. In Saskatchewan, Alberta, and northern 

 British Columbia, this species breeds in some areas of the aspen 

 parkland, as well as in the boreal forest of the northern portions of 

 these provinces. The parklands are characterized by "the dominance 

 of mature aspen growing in semiopen stands with occasional dense 

 groves of smaller aspens, scattered white spruce, white birch, and, in 

 the depressions along seepage courses, groves of willows" (Munro and 

 Cowan, 1947). Throughout most of the range, it appears that white- 

 throats nest in areas similar to those reported for Algonquin Park. 



Territory. — Males begin to sing and chase intruders from their 

 territories soon after arriving on the breeding grounds. On May 19, 

 1959, most birds in Algonquin Park were paired and territorial bound- 

 aries were well established. Chases and fights between males occur 

 frequently at the beginning of the breeding season but are seldom 

 seen in late June and July. Advertising song is given chiefly from a 

 few singing posts (see Voice). White-striped females occasionally 

 sing (see Voice) but otherwise females appear to take no part in adver- 

 tising or defending the territory. All the activities of the pair take 

 place in the territory until about the middle of July when most of the 

 young are becoming independent. After that males appear to be less 

 aggressive and territorial boundaries are disregarded. 



N. D. Martin (1960) censused a number of plots in Algonquin 

 Park several times each year. He found that densities of white- 

 throats varied from none in bog and hardwood forest to 56 territorial 

 males per 100 acres in a stand of balsam fir and white spruce. Areas 

 of 110 territories varied from 0.05 to 2.7 acres with an average of 

 0.52 acres. As these values are based on only a few observations of 

 each bird, they must be regarded as minimum estimates. Maire 

 Lainevool (unpublished data) carried out an intensive study of the 

 territories of 20 mated and 3 unmated males in an open coniferous 

 stand where the population density was about 25 territorial males per 

 100 acres. Each bird was watched for 1 to 4 hours in the morning 

 several times during the breeding season. Territory size tended to 



