BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Western Bluebird

TurdidaeForest birdsSialia mexicana

Western Bluebird has increased: up 43% on the route-weighted index since 1970.

+43%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
538RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
56Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

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 TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

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.

+29%Change by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.33Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.19–0.4695% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±38.3%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
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.19682029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20250.320.190.45
20260.320.190.45
20270.320.190.46
20280.320.190.46
20290.330.190.46

Where the Western Bluebird Is Detected

BBS routes recording Western Bluebird, sized by most recent count.

Western Bluebird Population Trend by State

Western Bluebird population trend by state.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Arizona+9%197040
California-18%1970189
Colorado+52%197163
Idaho-21%198413
Montana-32%198915
Nevadainsufficient datan/a5
New Mexico-18%197037
Oregon+74%197185
Texas+72%19744
Utah-20%197239
Washington+103%197039
Wyominginsufficient datan/a9

Western Bluebird Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Western Bluebird population trend by Bird Conservation Region.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Northern Pacific Rainforest-52%197072
Great Basin11×197073
Northern Rockies-29%197069
Sierra Nevada+40%197233
Southern Rockies / Colorado Plateau-32%1970134
Shortgrass Prairie-15%19987
Coastal California-3%1970107
Sonoran and Mojave Deserts-76%19705
Sierra Madre Occidental-4%197025
Chihuahuan Desert-80%197210

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.