For reasons that are not fully understood, these birds will occasionally interbreed and produce offspring. The resulting hybrids will display traits of both parents. Since the combinations of these plumage patterns vary widely from bird to bird, trying to figure out what you are looking at is often perplexing. For example, in the case of dark-eyed junco/white-throated sparrow hybrids, observers have reported birds with the wing pattern of a white-throated sparrow and the head pattern of a dark-eyed junco. Other birds look much like white-throated sparrows but sport the white outer tail feathers of dark-eyed junco.