Spot-Breasted Thrushes

     The six species of spot-breasted thrushes of eastern and northern North America, including gray-cheeked, Bicknell's, Swainson's and hermit thrushes, veeries and wood thrushes appear to be closely related.  All these thrush species are basically brown on top, which blends them into their forest floor homes, are American robin-shaped and average seven inches long.  Robins are thrushes, too, by the way. 
     Each kind of spot-breasted thrush has a dark, drooping "moustache" on each side of its face under its beak and dark spots scattered across its light-colored chest.  All of them have flute-like songs, nest in North American forests and winter in Central America and South America, where their common ancestor probably originated.  And all of them eat invertebrates they find on forest floors.  Only minor, probably recently-developed, differences separate them into distinct kinds.  Look for these thrushes in a field guide to American birds to see their similarities and differences.
     When their original ancestor raised young in different forest niches to have nesting room with less competition with their relatives for space and food, diverse kinds of thrushes, with slight changes in their appearances, developed from genetic quirks that were passed along to their descendants in isolated populations.  Over many years, the populations of each isolated group grew and became new species.  But most of the characteristics of these species today are still shared with each other.
     Gray-cheeked thrushes nest in coniferous forests across northern Canada and most of Alaska, and winter in South America.  This species is olive-gray on top and has gray cheeks.  The males' breezy songs roll down, but abruptly rise at the end.
     Bicknell's thrushes breed in the forested mountains of the Maritime Provinces, Catskill Mountains, Adironack Mountains and the wooded mountains of Vermont, New Hampshire and Maine.  This species winters in the West Indies.  And since they are very closely related to gray-cheeked thrushes, Bicknell's thrushes are almost identical to gray-cheeks and the songs of males of both kinds are similar.  The best way to distinguish these two types of thrushes is to note where they nest.
     Swainson's thrushes rear young in spruce forests across Canada and Alaska and in the northern Rocky Mountains of the United States.  They winter in Central and South America.  This olive-brown kind of thrush has a buffy face and a light ring around each eye.  Males' songs slide up the scale.
     Hermit thrushes hatch offspring in mixed coniferous/deciduous woods across Canada and southern Alaska, and on the Rocky Mountains.  They spend the northern winter in the southern half of the United Sates and Mexico, the only spot-breasted thrush to do so.
     Hermit thrushes have rusty tails, rather than the gray-brown tails of some of their relatives.  And they constantly pump their tails slowly up and down.
     Veeries raise youngsters on the leafy floors of damp, bottomland, deciduous woods in southern Canada, northern United States and the American Rockies.  They winter in Central and northern South America.  This species is completely rusty-brown above and has the least amount of spotting on its chest.  Males' breezy songs spiral down.
     Wood thrushes raise young in robin-like nurseries in shrubbery in deciduous woods in the eastern half of the United States.  Some wood thrush pairs hatch young in mature suburban areas with their many trees and shrubbery.  This type of thrush winters in Mexico and Central America.  The males' flute-like songs seem to say "a-o-lee" or "e-o lay".  This type of thrush has rusty heads and shoulders and the heaviest spotting on their chests of all their close relatives.
     Look for these six thrush species in summer when they are nesting in North America.  Or look them up in a field guide.  They are near look-alikes, which demonstrates their common ancestry not so long ago.