The Greater Snow Goose is dimorphic, meaning that it appears in two forms. Most Greater Snow Geese are called light morphs: they are white. Some are called dark morphs, or blue, geese: most of their feathers are blue-grey. The blue morph, which is quite common in Lesser Snow Geese, is rare in Greater Snow Geese: fewer than 4 percent of Greater Snow Geese are of this blue phase. Blue morph geese tend to mate with blues, and whites with whites
