Tuesday, December 20, 2016

Gray-cheeked vs Swainson’s Thrush

Gray-cheeked Thrush (7 September 2016) and Swainson’s Thrush (1 September 2016), two often difficult to identify species. These birds migrate through Northfield.

Generally Gray-cheeks lack the bright tan-colored eye rings of the Swainson’s Thrush. Some individuals are so similar that they have been thoguht to be hybrids. Genetic or other evidence of hybridization, however, is lacking.

I band more Swainson’s than Gray-cheeked thrushes. In their breeding range, Swainson's forage closer to the ground than Gray-cheeks, which may account for this difference. On small islands that lack Gray-cheeked Thrushes, Swainson’s forage higher in the forest (Mock and Yong 2000). I doubt, however, that these ecological differences are maintained during migration.

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