Swainson's Thrush    Catharus ustulatus

Migratory Status: Neotropical migrant

PIF Population Estimate: 100 000 000

Percent of western hemisphere population breeding in boreal forest: 59%

BAM Effective Detection Radius (m) : 93.56

PIF Maximum Detection Distance (m) : 200

Canadian BBS Population trend: -0.6 (-1.1 to -0.1)

Life History

To many, the song of the Swainson’s Thrush is one of the most beautiful and beloved. The series of upward spiralling, flute-like notes, especially in the early evening on a warm summer night, often symbolizes the dense and dark coniferous forests it inhabits. Given the species’ shy and secretive nature, the haunting song or common “whit-burrr” call is often the only contact that observers have with it.

The Swainson’s Thrush is a medium-sized songbird with reddish to grayish-brown back and wings, buff-coloured eye-ring, and white belly, with extensive dark-brown spotting on the upper breast and throat. As with many thrushes, males and females are identical in appearance. Given the wide distribution of the species North America, two distinct subspecies groups, each containing three subspecies, have been described. The “russet-backed” group is generally associated with populations near the Pacific coast, from Alaska to California, and “the olive-backed” group occupies the remainder of the breeding range.

The breeding range of the Swainson’s Thrush incorporates most of the forested regions of northern North America, from western Alaska east to Newfoundland. In the western United States breeding populations occur along the entire Pacific coast, with separate populations throughout the inter-mountain west. The breeding range continues as far south as Arizona and New Mexico, and east to western Wyoming and Colorado. Breeding also occurs throughout the mountainous regions of the northeastern United States, extending as far south as West Virginia, and possibly Virginia.

The wintering ranges, of the two subspecies groups described above are markedly different. Russet-backed populations winter throughout Central America, from central Mexico to eastern Panama. Olive-backed birds winter from western Colombia and Venezuela, south to north-western Argentina. Although unusual, there are occasional reports of birds wintering throughout continental North America.

The diet consists primarily of insects (spring and summer) and berries (fall and winter). Like many thrushes, foraging tends to occur close to, or near, the ground, but can occur as high as 8 m. Insects are mostly taken from within or above the leaf litter, whereas berries are often taken directly from fruiting trees or shrubs.

Reference(s)

Mack, D. E., and W. Yong. 2000. Swainson's Thrush (Catharus ustulatus), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/540