American Robin - Taxonomy

Taxonomy

This species was first described in 1766 by Carl Linnaeus in the twelfth edition of his Systema Naturae as Turdus migratorius. The binomial name derives from two Latin words: Turdus, 'thrush,' and migratorius from migrare 'to go.' The term robin for this species has been recorded since at least 1703. There are about 65 species of medium to large thrushes in the genus Turdus, characterized by rounded heads, longish pointed wings, and usually melodious songs. A study of the mitochondrial cytochrome b gene indicates that the American Robin is not part of the Central/South American clade of Turdus thrushes; instead it shows genetic similarities to the Kurrichane Thrush, T. libonyanus, and the Olive Thrush, T. olivaceus, both African species. This conflicts with a 2007 DNA study of 60 of 65 Turdus species which places the American Robin's closest relative as the Rufous-collared Robin (T. rufitorques) of Central America. Though having distinct plumage, the two species are similar in vocalization and behavior. Beyond this, it lies in a small group of four species of otherwise Central American distribution, suggesting it recently spread northwards into North America.

Seven subspecies of American Robin are recognized. These subspecies intergrade and are only weakly defined.

• T. m. migratorius, the nominate subspecies, breeds in the US and Canada, other than down the west coast, to the edge of the tundra from Alaska and northern Canada east to New England and then south to Maryland, North Carolina and northwest Virginia. It winters in southern coastal Alaska, southern Canada, most of the US, Bermuda, the Bahamas and eastern Mexico.

• T. m. nigrideus breeds from coastal northern Quebec to Labrador and Newfoundland and winters from southern Newfoundland south through most of the eastern US states to southern Louisiana, southern Mississippi and northern Georgia. It is uniformly darker or blackish on the head, with a dark gray back. The underparts are slightly more red than those of the nominate subspecies.

• T. m. achrusterus breeds from southern Oklahoma east to Maryland and western Virginia and south to northern Florida and the Gulf states. It winters through much of the southern part of the breeding range. It is smaller than the nominate subspecies. The black feathers of the forehead and crown have pale gray tips. The underparts are paler than those of the nominate subspecies.

• T. m. caurinus breeds in southeast Alaska through coastal British Columbia to Washington and northwest Oregon. It winters from southwest British Columbia south to central and southern California and east to northern Idaho. It is very slightly smaller than the nominate subspecies and very dark-headed. The white on the tips of the outer two tail feathers is restricted.

• T. m. propinquus breeds from southeast British Columbia, southern Alberta, southwest Saskatchewan south to southern California and northern Baja California. It winters throughout much of the southern breeding range and south to Baja California. It is the same size as or slightly larger than nominate T. m. migratorius, but paler and tinged more heavily brownish-gray. It has very little white on the tip of the outermost tail feather. Some birds, probably females, lack almost any red below. Males are usually darker and may show pale or whitish sides to the head.

• T. m. confinis breeds above 1000 meters (3300 ft) in the highlands of southern Baja California. This form is particularly distinctive, with pale gray-brown underparts. It is relatively small, and the palest subspecies, with uniform pale gray-brown on the head, face and upperparts. It usually lacks any white spots to the tips of the outer tail feathers, which have white edges. It is sometimes classed as a separate species, the San Lucas Robin, but the American Ornithologists' Union regards it as only a subspecies, albeit in a different group from the other races.

• T. m. phillipsi is resident in Mexico south to central Oaxaca. It is slightly smaller than propinquus but has a larger bill; the male's underparts are less brick-red than the nominate subspecies, and have a rustier tone.