Swainson's Thrush
Swainson's Thrush has surged: up 633% on the route-weighted index since 1968.
About the Swainson's Thrush
The Swainson's Thrush (Catharus ustulatus) is a North American member of the Thrushes (Turdidae). In this analysis it is grouped with the forest birds.
- Size
- 6–11 in long (15–28 cm) — a medium songbird (typical for the family)
- Habitat
- Woodlands and forest edges, including wooded suburbs and parks.
- Diet
- Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
- Range
- Recorded on 851 Breeding Bird Survey routes across 29 states, most concentrated in the Northern Pacific Rainforest.
- Family
- Turdidae · Forest birds
Notable Swainson's Thrush Trends
Swainson's Thrush has surged in surveyed states: up 633% on the route-weighted index since 1968.
Swainson's Thrush Population Forecast
If the recent trend holds, Swainson's Thrush is projected to rise about 26% by 2029 — from 2.8 in 2024 to a central estimate of 3.5 (95% range 2.8–4.2). A 5-year backtest shows a typical error of ±11.1%, with 100% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 3.3 | 2.7 | 4.0 |
| 2026 | 3.4 | 2.7 | 4.0 |
| 2027 | 3.4 | 2.8 | 4.1 |
| 2028 | 3.5 | 2.8 | 4.1 |
| 2029 | 3.5 | 2.8 | 4.2 |
Where the Swainson's Thrush Is Detected
BBS routes recording Swainson's Thrush, sized by most recent count.
Swainson's Thrush Population Trend by State
| Alaska | -6% | 1972 | 109 |
| Arizona | insufficient data | n/a | 1 |
| California | -19% | 1970 | 103 |
| Colorado | +200% | 1974 | 49 |
| Connecticut | insufficient data | n/a | 3 |
| Idaho | +133% | 1971 | 38 |
| Illinois | insufficient data | n/a | 1 |
| Maine | -52% | 1968 | 63 |
| Maryland | insufficient data | n/a | 1 |
| Massachusetts | -49% | 1970 | 4 |
| Michigan | +18% | 1973 | 33 |
| Minnesota | +202% | 1969 | 29 |
| Montana | +163% | 1970 | 45 |
| Nebraska | insufficient data | n/a | 1 |
| Nevada | insufficient data | n/a | 5 |
| New Hampshire | -4% | 1968 | 14 |
| New Mexico | insufficient data | n/a | 3 |
| New York | -39% | 1968 | 36 |
| North Carolina | insufficient data | n/a | 1 |
| Oregon | -28% | 1970 | 87 |
| Pennsylvania | -29% | 1969 | 17 |
| South Dakota | 18× | 1972 | 13 |
| Utah | -92% | 1975 | 29 |
| Vermont | +26% | 1968 | 16 |
| Virginia | insufficient data | n/a | 1 |
| Washington | -35% | 1970 | 82 |
| West Virginia | +61% | 1989 | 6 |
| Wisconsin | -53% | 1971 | 21 |
| Wyoming | -14% | 1970 | 40 |
Swainson's Thrush Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| BCR 2 | -59% | 1994 | 7 |
| BCR 4 | +14% | 1976 | 67 |
| Northern Pacific Rainforest | -13% | 1970 | 154 |
| Great Basin | -30% | 1970 | 66 |
| Northern Rockies | +49% | 1970 | 131 |
| Boreal Hardwood Transition | +190% | 1969 | 76 |
| Lower Great Lakes / St. Lawrence Plain | -38% | 1971 | 6 |
| Atlantic Northern Forest | -18% | 1968 | 119 |
| Sierra Nevada | +90% | 1974 | 16 |
| Southern Rockies / Colorado Plateau | +109% | 1972 | 79 |
| Badlands and Prairies | +986% | 1972 | 25 |
| Appalachian Mountains | +83% | 1969 | 33 |
| Coastal California | +29% | 1970 | 47 |
Swainson's Thrush Conservation Status
Our route-weighted index shows it up about 633% since 1968.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.