 The western Yukon fox sparrow (Passerella iliaca zaboria) differs from the nominate subspecies, the eastern fox sparrow (Passerella iliaca iliaca) only in having a grayer head and browner malar stripe on average.The morphological distinction between the subspecies is not pronounced and the birds are not resident all year; therefore positive identification within the red fox sparrow complex is often not possible in the field, at least in some regions.However, the populations occupy different ranges, apparently—as far as they can be distinguished—with just a small band of overlap.