As such, effects of brood parasitism are particularly severe in the Midwestern United States where cowbirds are in great abundance. Overall, these nests contained four times as many cowbird eggs as Wood Thrush eggs, leading one researcher to conclude that Wood Thrushes in Illinois are raising more cowbirds than they are their own species. In contrast, brood parasitism rates in the mid-Atlantic and Northeast are relatively low. The candle is burning at both ends for the Wood Thrush, as it is for many birds that breed in temperate North America and winter in the tropics of Latin America. At the same time that conditions on the breeding grounds are deteriorating, the tropical forests preferred by wintering Wood Thrushes are rapidly disappearing.
Wood Thrushes lead one of two lifestyles while on their wintering grounds.
As more forest is cleared, more birds will be forced to rely on inferior habitats, and fewer birds will live to make the next migration back to the United States. Nothing puts this into perspective better than a bird's-eye view. National Zoo Copyright 2001 All Worldwide Rights Reserved.