Canada goose (Branta canadensis sp.) feeding with Barnacle geese at Gruinart

The Cackling Goose was originally considered to be the same species or a subspecies of the Canada Goose, but in July 2004 the American Ornithologists' Union's Committee on Classification and Nomenclature split the two into two species, making Cackling Goose into a full species with the scientific name Branta hutchinsii. The British Ornithologists' Union followed suit in June 2005.

The AOU has divided the many subspecies between the two animals. To the present species were assigned:

Atlantic Canada Goose, Branta canadensis canadensis

Interior Canada Goose, Branta canadensis interior
Giant Canada Goose, Branta canadensis maxima

Moffitt's Canada Goose, Branta canadensis moffitti

Vancouver Canada Goose, Branta canadensis fulva

Dusky Canada Goose, Branta canadensis occidentalis

part of "Lesser complex", Branta canadensis parvipes

The distinctions between the two geese have led to confusion and debate among ornithologists. This has been aggravated by the overlap between the small types of Canada Goose and larger types of Cackling Goose. The old "Lesser Canada Goose" was believed to be a partly hybrid population, with the birds named taverneri considered a mixture of minima, occidentalis and parvipes. In addition, it has been determined that the Barnacle Goose is a derivative of the Cackling Goose lineage, whereas the Hawaiian Goose is an insular representative of the Canada.

(Wikipedia)