Hermit Thrush, Hagg Lake, Washington Co., Oregon on 17 December, 2010 by Greg Gillson.
The Hermit Thrush is the only spotted thrush expected in the Pacific NW in winter. They are one of the winter birds termed "half-hardy," such as the Lesser Goldfinch discussed a few weeks ago. They don't survive well if water stays frozen for more than a couple of days. Thus, their winter range in the Pacific NW is primarily west of the Cascades from southern British Columbia southward.
Hermit Thrushes in winter can be found in dense shrubbery in backyards and, especially, foothills. In this, they are found in similar winter habitats to Varied Thrushes. Both are shy birds, generally sticking to the shadows and brushy cover of conifer saplings.
The spotted thrushes are all very similar in appearance, with only slight differences.
In contrast to their plain plumage, most spotted thrushes (genus Catharis) have very complex and beautiful breeding songs. The name, Catharis, means "pure" and refers to the lovely melodius songs of this group. In fact, the Hermit Thrush is arguably the most beautiful singer of all North American birds. In winter, however, Hermit Thrushes are very quiet, giving only a blackbird-like "chuck" note that belies their extensive spring repertoire.
The difference between the calls of Hermit Thrushes and Varied Thrushes is slight. As mentioned, Hermit Thrush gives a "chuck" or "djuck" call. The call of Varied Thrush is slightly more mellow, "tchook" (with a long U sound, like "duke," not "book"). These soft calls are often the only indication that these birds are hiding nearby as you walk along the trail through the woods.
I am not the only one to have photographed and written about Hermit Thushes this winter. See the article by Dave Ingram on his Nature Island blog: Hello Hermit!.