Swainson's Thrush (Crum Woods Biodiversity Guide)

Swainson's Thrush

Catharus ustulatus

Summary ³

Swainson's Thrush (Catharus ustulatus), also called Olive-backed Thrush, is a medium-sized thrush. It is a member of Catharus genus and is typical of it in terms of its subdued coloration and beautiful voice. Swainson's Thrush was named after William Swainson, an English ornithologist.

Catharus ustulatus ⁴

Grayer overall than most of its North American relatives, Swainson’s Thrush (7 inches) is most easily separated from a similar species, the Gray-cheeked Thrush, by its buff-brown cheeks and conspicuous eye-rings. Other field marks include a spotted breast, pink legs, and a medium-length bill. Male and female Swainson’s Thrushes are similar to one another in all seasons. The Swainson’s Thrush breeds in Alaska and across a wide swath of central and southern Canada. Smaller numbers are found south of the Canadian border, particularly along the Pacific coast and at higher elevations in the Appalachians and the Rocky Mountains. Swainson’s Thrush winters in southern Mexico and Central America south to Argentina. In summer, Swainson’s Thrush breeds primarily in evergreen forests dominated by spruce and fir trees. During the winter, this species inhabits wet tropical forests. On migration, Swainson’s Thrush may be found in a variety of habitats with dense undergrowth available for foraging and cover. Many North American birders never travel far south enough to see Swainson’s Thrush in winter. This species is much easier to observe in summer and on migration, although it is more often heard than seen due to its preference for habitats with thick vegetation. Swainson’s Thrush may be observed foraging food while hopping along the forest floor or through the branches of trees. Swainson’s Thrush is most active during the day, but, like many migratory songbirds, this species migrates at night.

Habitat ⁵

Comments: Breeding habitat includes dense vegetation in coniferous forests, mixed hardwood-conifer forests (e.g., across Canada and northern New England, predominantly hardwood forests (e.g., in Northeast), riparian woodland and thickets of willow or alder (e.g., California and other western states at south end of range), aspen forests (e.g. southwest part of range), and sometimes coastal scrub (California) (Mack and Yong 2000). Depending on the location, this species may be associated with young, mature, or old growth (see Mack and Wong 2000). Range-wide, nesting occurs at elevations from sea level to 2,600 meters or higher. Nests usually are in small trees, close to the trunk, often 2 meters or less above ground; often in conifers, sometimes deciduous trees or shrubs (e.g., willow).

During migration, this species uses a wide range of wooded and shrubby habitats, generally with thick undergrowth.

During the boreal winter, Swainson's thrushes inhabit a wide range of conditions that may vary with region, including primary forest, mature selva forest, tropical semideciduous forest, humid to semihumid evergreen and semideciduous forest (including pine-oak, coniferous, tropical deciduous, and cloud forest), secondary growth, and forest-pasture edges, and human-made openings with ornamental shrubs (see Mack and Yong 2000).

Iucn red list assessment ⁶

Red List Category

Least Concern

Red List Criteria

Version

3.1

Year Assessed

2012

Assessor/s

BirdLife International

Reviewer/s

Butchart, S. & Symes, A.

Contributor/s

Justification

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

History

Least Concern (LC)
Least Concern (LC)
Least Concern (LC)
Lower Risk/least concern (LR/lc)
Lower Risk/least concern (LR/lc)
Lower Risk/least concern (LR/lc)

Sources and Credits

(c) Alejandro Bayer Tamayo, some rights reserved (CC BY-SA), https://www.flickr.com/photos/alejobayer/16209993949/
(c) Matt Reinbold from Bismarck, ND, USA, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Catharus_ustulatus_-North_Dakota-8a.jpg/460px-Catharus_ustulatus_-North_Dakota-8a.jpg
Adapted by Amanda Carrillo-Perez from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Catharus_ustulatus
(c) Smithsonian Institution, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34818115
(c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28917073
(c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34362704

More Info

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