Indeed, as Andy Stepniewski pointed out, the Swainson's Thrushes of the
South Cascades appear to be "Russet-backed" thrushes, the more reddish
subspecies. At Salmon la Sac this weekend the species was common at 3500'
in wet conifer forest with scattered broadleaf understory, and they were
obviously russet-backed by plumage and call. One bird gave a much stronger
"whit" call but defied our attempts to get a look at it. Either it was an
olive-backed or a russet-backed with an aberrant call.

Thus the population changes between Washington Pass and Snoqualmie Pass.
Somewhere inbetween, as you head north, russet-backs will give way to
olive-backs. I'll try to see if I can narrow this down further and, most
interesting, try to see the nature of the meeting, nonmeeting, or overlap
zone. Our single specimen from the Blue Mountains is an olive-backed.

Ian Paulsen told me Swainson's Thrushes were common at Sullivan Lake, Pend
Oreille County, which is relatively low and wet habitat, like that I
consider typical of russet-backed, rather than the high mountain conifer
forest where so far I've found olive-backed.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416