Western Bluebird
Western Bluebird has increased: up 43% on the route-weighted index since 1970.
About the Western Bluebird
The Western Bluebird (Sialia mexicana) 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 538 Breeding Bird Survey routes across 12 states, most concentrated in the Southern Rockies / Colorado Plateau.
- Family
- Turdidae · Forest birds
Notable Western Bluebird Trends
No notable trend signals for Western Bluebird. See the full index history below.
Western Bluebird Population Forecast
If the recent trend holds, Western Bluebird is projected to rise about 29% by 2029 — from 0.25 in 2024 to a central estimate of 0.33 (95% range 0.19–0.46). A 5-year backtest shows a typical error of ±38.3%, with 80% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.32 | 0.19 | 0.45 |
| 2026 | 0.32 | 0.19 | 0.45 |
| 2027 | 0.32 | 0.19 | 0.46 |
| 2028 | 0.32 | 0.19 | 0.46 |
| 2029 | 0.33 | 0.19 | 0.46 |
Where the Western Bluebird Is Detected
BBS routes recording Western Bluebird, sized by most recent count.
Western Bluebird Population Trend by State
| Arizona | +9% | 1970 | 40 |
| California | -18% | 1970 | 189 |
| Colorado | +52% | 1971 | 63 |
| Idaho | -21% | 1984 | 13 |
| Montana | -32% | 1989 | 15 |
| Nevada | insufficient data | n/a | 5 |
| New Mexico | -18% | 1970 | 37 |
| Oregon | +74% | 1971 | 85 |
| Texas | +72% | 1974 | 4 |
| Utah | -20% | 1972 | 39 |
| Washington | +103% | 1970 | 39 |
| Wyoming | insufficient data | n/a | 9 |
Western Bluebird Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| Northern Pacific Rainforest | -52% | 1970 | 72 |
| Great Basin | 11× | 1970 | 73 |
| Northern Rockies | -29% | 1970 | 69 |
| Sierra Nevada | +40% | 1972 | 33 |
| Southern Rockies / Colorado Plateau | -32% | 1970 | 134 |
| Shortgrass Prairie | -15% | 1998 | 7 |
| Coastal California | -3% | 1970 | 107 |
| Sonoran and Mojave Deserts | -76% | 1970 | 5 |
| Sierra Madre Occidental | -4% | 1970 | 25 |
| Chihuahuan Desert | -80% | 1972 | 10 |
Western Bluebird Conservation Status
Our route-weighted index shows it up about 43% since 1970.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.