Assortative mating in the dimorphic lesser snow goose could be explained if birds choose mates according to the color of their parents. Young birds were tested to determine if they would show color preferences at an early age. Blue and white phase lesser snow geese, as well as white phase geese dyed pink, were reared in families with either a blue, white, or pink foster parent. All birds were then combined in a large flock in an attempt to simulate natural conditions as closely as possible. Birds tested in a choice situation were found to show a significant preference for birds of the same color as their foster parents. The fact that the young were raised in families and later in a flock suggested that color preferences were a natural and not a laboratory phenomenon.Two lines of evidence suggest that where the color of the foster parent is altered, the preference for the color of the original foster parent is lost. This suggests that prolonged association of gosling and parent is important if parental color is to have an influence on mate selection.