“Perhaps more than any other, I think, the present species epitomizes the genus, as known in the southern and central states, as furtive, wraithlike, wide-eyed observers in the new-leafed forests. The Gray-cheeked Thrush is better represented in the Kentucky forests than in the literature . . . ”
Mengel 1965b : 364
Breeding in taiga and adjacent tundra from Newfoundland to eastern Siberia, the Gray-cheeked Thrush may be North America's least-known Catharus thrush. Few ornithologists visit its remote breeding habitats, and fewer still have studied its natural history and ecology. The species shows considerable geographic overlap with 4 other thrushes, including 2 congeners—Swainson's Thrush (C. ustulatus) and Hermit Thrush (C. guttatus). Nesting habitats of these thrushes differ, however, with the Gray-cheeked Thrush primarily a bird of brushy willow-alder thickets and low spruce forests with dense undergrowth. A relatively shy species, especially during migration, the Gray-cheeked Thrush is less retiring on breeding territories and during subarctic twilight activity periods. Birders are more likely to hear this species' nocturnal flight call during spring and fall migration than to observe migrants on the ground.
The Gray-cheeked Thrush is similar in appearance to several other Catharus species, especially Bicknell's Thrush (C. bicknelli), which was only recently separated as a distinct species from the Gray-cheeked ( Ouellet 1993 ). In fact, much of the published information on “Gray-cheeked Thrush” has been based on the work of Wallace ( Wallace 1939 ) and Dilger ( Dilger 1956c , Dilger 1956b ), who studied populations of Bicknell's Thrush. Bent's Life Histories ( Bent 1949 ) devotes only 10 pages to Gray-cheeked Thrush, compared to 18 pages for Bicknell's Thrush; here, we also draw considerable information from studies of Bicknell's Thrush (see Rimmer et al. 2001 ). Surprisingly little research has been conducted on the Gray-cheeked Thrush, either on its breeding or wintering grounds. Information on the species' breeding biology is limited largely to anecdotal observations, while published data on its winter ecology, habitat use, and behavior are virtually nonexistent. Clearly this is a thrush that deserves more extensive research and attention.