Gray-cheeked Thrush

The gray-cheeked thrush is a medium-sized thrush. This species is 15–17 cm (5.9–6.7 in) in length, and has the white-dark-white underwing pattern characteristic of Catharus thrushes. It is a member of a close-knit group of migrant species together with the veery and Bicknell's thrush; it forms a cryptic species pair with the latter. The gray-cheeked thrush is all but indistinguishable from Bicknell's thrush except by its slightly larger size and different song. The two were formerly considered conspecific. Of all the American spotted thrushes, the gray-cheeked has the most northern breeding range.

Source: Wikipedia