Catharus ustulatus - (Nuttall, 1840)
Swainson's Thrush
Other English Common Names: Swainson's thrush
Other Common Names: Sabiá-de-Óculos
Taxonomic Status: Accepted
Related ITIS Name(s): Catharus ustulatus (Nuttall, 1840) (TSN 179788)
French Common Names: grive à dos olive
Spanish Common Names: Zorzal de Swainson, Zorzal Boreal
Unique Identifier: ELEMENT_GLOBAL.2.100960
Element Code: ABPBJ18100
Informal Taxonomy: Animals, Vertebrates - Birds - Perching Birds
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Passeriformes Turdidae Catharus
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online: http://www.aou.org/.
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Catharus ustulatus
Taxonomic Comments: Formerly placed in genus Hylocichla (AOU 1983). Composed of two groups: swainsoni (Olive-backed Thrush) and ustulatus (Russet-backed Thrush) (AOU 1998).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 07Apr2016
Global Status Last Changed: 03Dec1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Wide nesting range in North America; numerous subpopulations; large population size; slow rate of decline over the past several decades; major threat is habitat loss, degradation, and fragmentation in breeding range and winter range.
Nation: United States
National Status: N5B (19Mar1997)
Nation: Canada
National Status: N5B,N5M (25Jan2018)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (SNRM), Alaska (S5B), Arizona (S1), Arkansas (SNA), California (SNR), Colorado (S5B), Connecticut (SNA), Delaware (SNA), District of Columbia (S4N), Florida (SNA), Georgia (SNRN), Idaho (S5B), Illinois (SNA), Indiana (SNA), Iowa (S4N), Kansas (SNA), Kentucky (SNA), Louisiana (SNA), Maine (S5B), Maryland (SHB), Massachusetts (S2B,S5N), Michigan (S3S4), Minnesota (SNRB), Mississippi (SNA), Missouri (SNA), Montana (S5B), Navajo Nation (S1S2B), Nebraska (SU), Nevada (S3B), New Hampshire (S5B), New Jersey (SNA), New Mexico (S3B,S4N), New York (S5B), North Carolina (S1B,S5N), North Dakota (SNA), Ohio (SNA), Oklahoma (S4N), Oregon (S4S5B), Pennsylvania (S2S3B,S5N), Rhode Island (SNA), South Carolina (SNA), South Dakota (S4B), Tennessee (S5N), Texas (S4), Utah (S3S4B), Vermont (S4B), Virginia (S1B), Washington (S5B), West Virginia (S3B), Wisconsin (S2B), Wyoming (S5B)
Canada Alberta (S5B), British Columbia (S5B), Labrador (S5B,S5M), Manitoba (S5B), New Brunswick (S5B,S5M), Newfoundland Island (S5B,S5M), Northwest Territories (S5B), Nova Scotia (S3S4B), Ontario (S4B), Prince Edward Island (S4B), Quebec (S5), Saskatchewan (S5B), Yukon Territory (S5B)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: Nesting range extends from western and central Alaska across all of Canada (north to north-central Yukon, southern Northwest Territories (Great Bear Lake), northern Manitoba, nnorthern Ontario, north-central Quebec to about 54°N, central Labrador, and northern Newfoundland), and south through Pacific coast states to southern California, south through the Rocky Mountains to Arizona and northern New Mexico, south in the Great Plains and Great Lakes regions to eastern Montana, Black Hills of South Dakota, southern Saskatchewan, and northern Minnesota, and south in eastern North America to northern Pennsylvania, New England, and disjunctly to Virginia (Mack and Yong 2000). Range during the northern winter is mainly in Mexico and northern South America (east of the Andes in Colombia, Venezuela, Ecuador, eastern Peru, northern and eastern Bolivia, and northwestern Argentina, with a few records from western Amazonian Brazil and coastal southwestern Peru) (Ridgely and Tudor 1989); also occurs in smaller numbers in Central America (Mack and Yong 2000).

Number of Occurrences: > 300
Number of Occurrences Comments: This species is represented by a large number of occurrences (subpopulations).

Population Size: >1,000,000 individuals
Population Size Comments: Total adult population size is unknown but certainly exceeds 1,000,000. Rich et al. (2004) estimated population size at 100,000,000.

Number of Occurrences with Good Viability/Integrity: Very many (>125)

Overall Threat Impact: Medium
Overall Threat Impact Comments: Primary threat is habitat loss, degradation, and fragmentation affecting portions of the breeding range and wintering range (see review by Mack and Yong 2000).

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Breeding Bird Survey (BBS) data for 1980-2007 indicate a range-wide statistically significant decline of 0.8% per year, primarily reflecting a decline in Canada (no significant trend in the United States). Time frame for short-term trend (three generations) is roughly 18 years; over that period BBS data indicate very little change in abundance (number of birds per route).

Long-term Trend: Decline of <30% to increase of 25%
Long-term Trend Comments: Declines in distribution have been noted in California (see Mack and Yong 2000) and Massachusetts (Veit and Petersen 1993).

This species appears to have undergone a slow long-term decline. Breeding Bird Survey (BBS) data for 1966-2007 indicate a range-wide statistically significant decline of 0.6% per year. The same rate of decline applies to both the United States and Canada, but the trend is significant only for Canada.

Other NatureServe Conservation Status Information

Distribution
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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Nesting range extends from western and central Alaska across all of Canada (north to north-central Yukon, southern Northwest Territories (Great Bear Lake), northern Manitoba, nnorthern Ontario, north-central Quebec to about 54°N, central Labrador, and northern Newfoundland), and south through Pacific coast states to southern California, south through the Rocky Mountains to Arizona and northern New Mexico, south in the Great Plains and Great Lakes regions to eastern Montana, Black Hills of South Dakota, southern Saskatchewan, and northern Minnesota, and south in eastern North America to northern Pennsylvania, New England, and disjunctly to Virginia (Mack and Yong 2000). Range during the northern winter is mainly in Mexico and northern South America (east of the Andes in Colombia, Venezuela, Ecuador, eastern Peru, northern and eastern Bolivia, and northwestern Argentina, with a few records from western Amazonian Brazil and coastal southwestern Peru) (Ridgely and Tudor 1989); also occurs in smaller numbers in Central America (Mack and Yong 2000).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, AL, AR, AZ, CA, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NN, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, LB, MB, NB, NF, NS, NT, ON, PE, QC, SK, YT

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: NatureServe, 2002; WWF-US, 2000


U.S. Distribution by County Help
State County Name (FIPS Code)
AZ Apache (04001), Cochise (04003), La Paz (04012), Maricopa (04013), Mohave (04015), Pima (04019), Santa Cruz (04023)
NC Mitchell (37121)
PA Elk (42047), Forest (42053), Luzerne (42079), Lycoming (42081), McKean (42083), Potter (42105), Sullivan (42113), Warren (42123)
VA Grayson (51077)*, Smyth (51173)*
WI Ashland (55003), Bayfield (55007), Florence (55037), Forest (55041), Iron (55051), Sawyer (55113), Vilas (55125)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Upper Susquehanna-Tunkhannock (02050106)+, Upper Susquehanna-Lackawanna (02050107)+, Sinnemahoning (02050202)+, Lower West Branch Susquehanna (02050206)+
04 Beartrap-Nemadji (04010301)+, Bad-Montreal (04010302)+, Brule (04030106)+, Menominee (04030108)+
05 Upper Allegheny (05010001)+, Middle Allegheny-Tionesta (05010003)+, Clarion (05010005)+, Upper New (05050001)+*
06 South Fork Holston (06010102)+*, Nolichucky (06010108)+
07 Namekagon (07030002)+, Upper Chippewa (07050001)+, Flambeau (07050002)+, South Fork Flambeau (07050003)+, Upper Wisconsin (07070001)+
14 Chinle (14080204)+
15 Little Colorado headwaters (15020001)+, Havasu-Mohave Lakes (15030101)+, Sacramento Wash (15030103)+, Imperial Reservoir (15030104)+, Upper San Pedro (15050202)+, Upper Santa Cruz (15050301)+, Brawley Wash (15050304)+, Hassayampa (15070103)+, Whitewater Draw (15080301)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Reproduction Comments: Clutch size usually is 3-4. Incubation, by female, lasts 10-14 days. Young are tended by both parents, leave nest at 10-14 days.
Ecology Comments: Nonbreeding: solitary or in loose flocks in migration (Stiles and Skutch 1989, Rappole and Warner 1980).
Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: Y
Mobility and Migration Comments: Abundant migrant in Costa Rica, mid-September to November and April-late May (Stiles and Skutch 1989). Most common migrant thrush in Colombia; transient and winter resident in South America early October-late April (Hilty and Brown 1986).
Palustrine Habitat(s): FORESTED WETLAND, Riparian
Terrestrial Habitat(s): Forest - Conifer, Forest - Hardwood, Forest - Mixed, Forest/Woodland, Shrubland/chaparral, Woodland - Conifer, Woodland - Hardwood, Woodland - Mixed
Habitat 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).

Adult Food Habits: Frugivore, Invertivore
Immature Food Habits: Frugivore, Invertivore
Food Comments: Eats insects and other invertebrates, small fruits, seeds (Terres 1980). Very frugivorous in migration and during northern winter, sometimes concentrates in large numbers near fruiting trees and shrubs (Hilty and Brown 1986). In Costa Rica, eats many fruits and arillate seeds, relatively few insects and other invertebrates; may forage along edge of army ant swarms (Stiles and Skutch 1989).
Adult Phenology: Circadian, Crepuscular, Diurnal
Immature Phenology: Circadian, Crepuscular, Diurnal
Phenology Comments: May sing day and night in Alaska.
Length: 18 centimeters
Weight: 31 grams
Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation
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Group Name: Passerines

Use Class: Breeding
Subtype(s): Foraging Area, Nest Site, Nesting Colony
Minimum Criteria for an Occurrence: Evidence of historical breeding, or current and likely recurring breeding, at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Mapping Guidance: Breeding occurrences include nesting areas as well as foraging areas.

For swallows and other species that have separate nesting and foraging areas, separations are based on nest sites or nesting areas, not to locations of foraging individuals. For example, nesting areas separated by a gap larger than the separation distance are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Mean foraging radius (from nesting area) of Brown-headed Cowbird females was 4.0 kilometers in California, 1.2 kilometers in Illinois-Missouri (Thompson 1994). Yellow-headed Blackbirds, Brewer's Blackbirds, and probably Red-winged Blackbirds all forage up to 1.6 kilometers away from breeding colony (Willson 1966, Horn 1968). In one study, Brewer's Blackbirds were found as far as 10 kilometers from nesting area (Williams 1952), but this may be unusual.

For swallows and other parrerines with similar behavioral ecology, separation distance pertains to nest sites or nesting colonies, not to locations of foraging individuals. For example, nesting areas separated by a gap of more than 5 km are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.

Use Class: Migratory stopover
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: For most passerines: Evidence of recurring presence of migrating individuals (including historical) and potential recurring presence at a given location; minimally a reliable observation of 25 birds in appropriate habitat.

For swallows: Evidence of recurring presence of migrating flocks (including historical) and potential recurring presence at a given location; minimally a reliable observation of 100 birds in appropriate habitat (e.g., traditional roost sites).

Occurrences should be locations where the species is resident for some time during the appropriate season; it is preferable to have observations documenting presence over at least 7 days annually.

EOs should not be described for species that are nomadic during nonbreeding season: e.g., Lark Bunting.

Be cautious about creating EOs for observations that may represent single events.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance somewhat arbitrary but intended to define occurrences of managable size for conservation purposes. Occurrences defined primarily on the basis of areas supporting concentrations of birds, rather than on the basis of distinct populations.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G., and S. Cannings

Use Class: Nonbreeding
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: Any area used traditionally in the nonbreeding season (used for populations that are not resident in a location year-round). Minimally, reliable observations of 10 or more individuals in appropriate habitat for 20 or more days at a time. For G1-G3 species, observations of fewer individuals could constitute an occurrence of conservation value. Sites used during migration should be documented under the 'migratory stopover' location use class.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance is necessarily arbitrary but attempts to balance the high mobility of birds with the need for occurrences of reasonable spatial scope. Note that a population's roost sites and foraging areas are parts of the same occurrence, even if they are more than 5 km apart.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G.

Use Class: Nonmigratory
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a particular location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in or near appropriate habitat.

These occurrence specifications are used for nonmigratory populations of passerine birds.

Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and breeding-season foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Blue jays have small summer home ranges but fly up to 4 kilometers to harvest mast (Tarvin and Woolfenden 1999). Flocks of pinyon jays range over 21-29 square kilometers (Ligon 1971, Balda and Bateman 1971); nesting and foraging areas may be widely separated. Tricolored blackbirds forage in flocks that range widely to more than 15 kilometers from the nesting colony (Beedy and Hamilton 1999).

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.
Notes: These specs pertain to nonmigratory species.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 06Mar2009
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 06Mar2009
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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