Greylag goose the western greylag goose, breeds in Iceland and north and central Europe; "A. a. rubrirostris", the eastern greylag goose, breeds in Romania, Turkey and Russia eastwards to northeastern China. The two subspecies intergrade where their ranges meet. The greylag goose sometimes hybridises with other species of goose including the barnacle goose ("Branta leucopsis") and the Canada goose ("Branta canadensis"), and occasionally with the mute swan ("Cygnus olor"). The greylag goose was one of the first animals to be domesticated; this happened at least 3000 years ago in Ancient Egypt, the domestic breed being known as "A. a. domesticus". As the
Canada goose the cackling goose, which slightly overlap in mass. However, most subspecies of the cackling goose (exclusive of Richardson's cackling goose, "B. h. hutchinsii") are considerably smaller. The smallest cackling goose, "B. h. minima", is scarcely larger than a mallard. In addition to the size difference, cackling geese also have a shorter neck and smaller bill, which can be useful when small Canada geese comingle with relatively large cackling geese. Of the "true geese" (i.e. the genera "Anser", "Branta" or "Chen"), the Canada goose is on average the largest living species, although some other species that are geese in name, if