Rusty blackbird (Euphagus carolinus) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

The English name for the species Euphagus carolinus Müller (1776) is the Rusty Blackbird. The French name is Quiscale rouilleux. Its taxonomy is as follows:

Two species of blackbirds of the genus Euphagus occur in North America: Rusty Blackbird and Brewer’s Blackbird (E. cyanocephalus; American Ornithologists’ Union 1998). The genus Euphagus is believed to be more closely related to the genus Quiscalus than to the genus Agelaius (Lanyon 1994).

There are two recognized subspecies of Rusty Blackbird: E. c. carolinus, which occurs throughout most of the species’ range, and E. c. nigrans (Burleigh and Peters 1948), which breeds in Newfoundland and Labrador, Nova Scotia and the Magdalen Islands in Québec (Godfrey 1986; American Ornithologists’ Union 1998). While E. c. nigrans is generally darker in the body and has a blue sheen to the head, the differences between its plumage and that of E. c. carolinus are small when individual variation is taken into consideration (Pyle 1997). This status report covers E. carolinus and its subspecies.

Morphological description

The Rusty Blackbird is a medium-sized passerine (body length: 21-25 cm; body mass: 64 g), with relatively long, narrow, pointed wings, and a fine, slightly curved bill (Godfrey 1986). Both sexes have pale yellow eyes, black bills that are shorter than the head and entirely black feet. The tail is similar in length to the wings and is slightly rounded. During the breeding season, the adult male is uniformly black, with a faint greenish gloss on the body and slight violet gloss on the head and neck. In fall, the plumage changes slightly, with the edges of the tertiary feathers, scapulars, wing coverts and the head, breast and back feathers becoming rust coloured (Pyle 1997). The plumage of the female during the breeding season is brownish grey, with no gloss (Pyle 1997). The winter plumage of the female differs from the breeding plumage, being generally rust coloured, with a dark grey back, tail and wings. The edges of the tertiary feathers, scapulars and the coverts are rust coloured. In the fall, the characteristics of immature birds (i.e., feathers and iris colour) are similar to those of adults (Pyle 1997), although young juveniles have a dark iris.

The Rusty Blackbird can sometimes be confused with the Brewer’s Blackbird, which is similar in size and colouring (Avery 1995). The plumage of the male Brewer’s Blackbird is more glossy than that of the Rusty Blackbird. The Brewer’s Blackbird also has a violet and greenish gloss on the head, but has a shorter, straighter, and thicker bill than the Rusty Blackbird (Avery 1995). Moreover, the Brewer’s Blackbird’s legs and tail are generally longer than those of the Rusty Blackbird (Avery 1995). The females of both species differ in the colouring of their iris; the Rusty Blackbird’s iris is yellow whereas the Brewer’s Blackbird’s is dark (Avery 1995). The females of both species also differ in overall colouring, which is grey for the Rusty Blackbird, and rather brown for the Brewer’s Blackbird (Avery 1995).

Genetic description

Few molecular or genetic studies have been conducted on the relationships between the Rusty Blackbird and other species or subspecies (Lanyon and Omland 1999).