VARIATIONS IN HYLOCICHLA USTULATA — BOND 385 



western hemlock, western red cedar, and grand fir. Subclimax asso- 

 ciates are dominated by Douglas-fir. 



H. u. swainsoni prefers both climax and subclimax forests of the 

 Canadian Zone. Their habitat requirements show some variation in 

 different parts of their range, for, according to Bent (1949, p. 175), 

 "this thrush is less common in mature dense coniferous forests than 

 in bordering growths of smaller trees, where young balsam firs are 

 growing up with a mixture of birches." Again, referring to northern 

 New England, he said "they prefer the spruce and fir forests of the 

 Canadian Zone." 



H. u. almae occupies a broad range of climax and subclimax forested 

 areas across the Canadian, Transition, and lower Hudsonian Zones. 

 Among the dominants found in this area are black, white, and Engle- 

 mann spruce and lodgepole pine. 



H. u. oedica prefers the less humid areas of the Pacific Coast States 

 and is found in the Transition Zone where yellow pine predominates 

 and where strips of willow, cottonwood, and white alder provide 

 nesting sites along foothill, valley, and streamside lowlands. 



Summary 



To reevaluate the criteria purported to be significant in segregating 

 the various races of Swainson's thrush 513 specimens were assembled. 

 Birds from Alaska south through the Rocky Mountains to Colorado 

 were found to have a grayish-olive dorsal coloration, while the upper- 

 parts of birds from the Athabaska River in Alberta eastward to New- 

 foundland and south to West Virginia exhibited a more reddish- 

 olive coloration. 



Hylocichla ustulatxi oedica Oberholser is considered a valid race 

 and as a consequence the nominate form H. u. ustulata is restricted 

 to the Pacific coast from northwestern Oregon to Juneau, Alaska. 



The terminal population, H. u. clarescens, described by Burleigh 

 and Peters from Newfoundland, is not considered sufficiently distinct 

 from the mainland form H. u. swainsoni to be given nomenclatural 

 recognition. The subspecies H. u. incana, described by Godfrey in 

 1951 from the Yukon Territory, is considered a synonym of H. u. 

 almae Oberholser, 1898. 



H. u. almae does not normally occur along the Atlantic coast during 

 migration. There are, however, a number of records from southern 

 Illinois and the Gulf States which suggest that the Mississippi Valley 

 may be a major fly way for this subspecies in the spring and fall. 



Several specimens labelled ^^ ustulata" taken along the Atlantic 

 and Gulf coasts were found to be foxed specimens of swainsoni. This 

 error suggests that all former records of the Pacific coast race taken 

 in the east should be re-examined for possible misidentification. 



