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Geographic VariationSize varies little across the species’ circumpolar range, but plumage color and saturation differ considerably. Variation in the color of the belly is the most striking characteristic, as is this color’s contrast with the black breast: a light gray belly is typical of birds that breed in e. North America and across the n. Atlantic, whereas a blackish belly is typical of birds that breed in w. low Arctic of North America and central and e. Russian Arctic; birds that breed in the high Arctic of w. Canada are variably intermediate, with a medium to dark gray belly (Boyd and Maltby 1979, Boyd et al. 1988, Buckley and Mitra 2002). The width of the white necklace narrows from west to east across North America and the n. Atlantic (Boyd and Maltby 1979), although individual variation is considerable: on the Atlantic Coast of the United States, a high frequency of birds in New Jersey had the necklace complete (i.e., encircling the neck), whereas birds in New York and Virginia had the necklace broken or incomplete (Vangilder and Smith 1985), a difference that may associate with a genetic divergence or a separate breeding population (Novak et al. 1989).
SubspeciesThree extant subspecies recognized: B. b. bernicla, B. b. hrota, and B. b. nigricans, though only latter two are resident to N. America. Subspecific designation of B. b. hrota and B. b. nigricans is based on differences in physical appearance and division of breeding and wintering grounds; mitochondrial and nuclear genetic markers support this distinction (S. Talbot et al. unpubl. data). Beyond these subspecies designations, other divisions are commonly used to describe distinct ecological stocks based on breeding and wintering locations. Therefore, in addition to the 3 subspecies, we also recognize 4 stocks of Brant that breed in North America (Fig. 2, named and numbered below).B. b. bernicla: (Linnaeus, 1758), the Dark-bellied Brant or Dark-bellied Brent Goose. Breeds in central Russian Arctic, winters in w. Europe. Similar to B. b. hrota, but belly a darker brownish gray that contrasts less with the breast; white fringes on sides narrower, especially towards breast; dark gray dorsum becoming ashy-gray over winter (grayer than B. b. hrota); necklace broken in front and relatively narrow.B. b. hrota: (Müller, 1776), the Atlantic Brant, Light-bellied Brant, or Pale-bellied Brent Goose. Breeds in e. North American Arctic, also n. Greenland, Spitsbergen, and Franz Josef Land. Pale, grayish-brown belly contrasts sharply with black breast; white fringes on sides broaden from breast to flanks; dorsum distinctly brown; necklace often broken in front. Includes 2 stocks in North America: (1) “Atlantic Brant” breeding in e. Canadian low and mid-Arctic, near Foxe Basin and wintering on Atlantic Coast between Massachusetts and N. Carolina (Bellrose 1980, Kirby and Obrecht 1982, Gaston et al. 1986); (2) “Eastern High-Arctic Brant” breeding on e. Canadian high-Arctic islands and wintering primarily in Ireland (Maltby-Prevett et al. 1975, O’Briain and Healy 1991).B. b. nigricans: (Lawrence, 1846), the Black Brant. Breeds from w. North America low Arctic to e. Russian Arctic. Blackish belly shows weak contrast with breast; white fringes on flanks broad but restricted to rear flanks and forming noticeable white flank patch; very dark brown upperparts (blacker than B. b. hrota); more prominent, taller, and usually complete necklace. Includes the third North American stock: (3) “Black Brant” breeding in w. Canadian low Arctic (including Banks and Victoria Is.) and n. and w. Alaska and wintering along the Pacific Coast from Alaska to Mexico (Bellrose 1980, Subcommittee on Pacific Brant 2002, Sedinger et al. 1993). Included here as a synonym is the name B. b. orientalis given to populations breeding in ne. Siberia (Lena to Anadyr) but west of the Chukchi Peninsula populations; said to be paler than B. b. nigricans, but this has been attributed to individual variation by Portenko (1981). The original naming of B. b. nigricans is based on a type specimen from Egg Harbor, NJ, even though B. b. nigricans are restricted to the Pacific Coast during winter, resulting in some taxonomic uncertainty. This type specimen had an intermediate gray belly, leading Buckley and Mitra (2002) to suggest it was a “Western High-Arctic Brant” or “Gray-bellied Brant” (see below), not a Black Brant. Adding to the debate, Delacour and Zimmer (1952) considered B. b. nigricans to be an additional dark-bellied race called Lawrence’s Brant, using name B. b. orientalis for all other Black Brant. Regardless of taxonomy of original type specimen, B. b. nigricans has been firmly established as the subspecies designation for Black Brant (American Ornithologists’ Union [AOU] 1998).A fourth group with no AOU-assigned subspecies designation, commonly referred to as Gray-bellied Brant, constitutes the fourth stock in North America: (4) “Western High-Arctic Brant” ((Boyd and Maltby 1979, Boyd et al. 1988, Reed et al. 1989a, 1989b, Shields 1990). These birds have a medium to dark gray belly, intermediate between B. b. hrota and B. b. nigricans, that contrasts with their black breast (Boyd et al. 1988). Neck collar extent is variable, ranging from interrupted as in B. b. hrota, to completely encircling the neck as in B. b. nigricans. Breeds on the Parry Islands (Melville, Prince Patrick, and Borden) in the high Arctic of w. Canada and winters on Puget Sound of the Pacific Coast (Boyd and Maltby 1979, Reed et al. 1989a), although a few winter records are from the Atlantic Coast (Delcour and Zimmer 1952, Buckley and Mitra 2002). The distinct plumage and breeding and wintering locations of this stock are suggestive of a discrete subspecies; however, mitochondrial and nuclear genetic markers fail to support the assignment of subspecies distinction (S. Talbot et al. unpubl. data). Gray-bellied Brant appear intermediate between B. b. hrota and B. b. nigricans, demonstrating genetic characteristics consistent with admixture from both recognized North American subspecies. This is consistent with the location of their breeding area, which is geographically intermediate between those of B. b. hrota and B. b. nigricans.
Related SpeciesThe order Anseriformes is speciose lineage of familiar birds, the ducks, geese, and swans (Anatidae), as well as the less familiar trio of screamers (Anhimidae) of South America and the Magpie Goose (Anseranatidae: Anseranas semipalmata) of Australia and New Guinea. Within the waterfowl lineage (Anatidae, sensu Livezey 1997), the true geese and swans are closely related and generally placed in the same subfamily, Anserinae (e.g., Am. Ornithol. Union 1998).Among the geese—the tribe Anserini—the genus Branta is a sister clade of Chen and Anser. Within Branta, which is distinguished from other geese by the black feet and bill and by black and white markings on head and neck (Ogilivie 1978), B. bernicla is either sister to small Old World species in the genus (e.g., B. leucopsis, the Barnacle Goose, and B. ruficollis, the Red-breasted Goose; Livezey 1996), or is basal to other species (Gonzalez et al. 2009). The species is estimated to have diverged from a common ancestor with B. canadensis, the ubiquitous Canada Goose, roughly 4 mya (Van Wagner and Baker 1990). Various hybrids between B. bernicla and other species of geese, mostly in captivity, have been documented (McCarthy 2006).
Lewis, T. L., D. H. Ward, J. S. Sedinger, A. Reed and D. V. Derksen. 2013. Brant (Branta bernicla), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/337