BirdAnalyst
Species · Colorado · BBS 2026 Release · 1966–2025

Brewer's Blackbird Population Trend in Colorado

All statesGeneralists

Brewer's Blackbird in Colorado has fallen sharply: down 58% on the route-weighted index since 1970.

-58%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 →
143Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brewer's Blackbird Trends in ColoradoNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Brewer's Blackbird has fallen sharply in Colorado: down 58% on the route-weighted index since 1970.

Brewer's Blackbird Population Forecast in Colorado

If the recent trend holds, Brewer's Blackbird in Colorado is projected to fall about 70% by 2030 — from 7.2 in 2025 to a central estimate of 2.2 (95% range 0.00–15). A 5-year backtest shows a typical error of ±43.6%, with 100% of held-out values landing inside the 95% band.

-70%Change by 2030TrendPercent 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 →
2.2Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1595% 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 →
±43.6%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, Brewer's Blackbird in Colorado is projected to fall about 70% by 2030 — from 7.2 in 2025 to a central estimate of 2.2 (95% range 0.00–15). A 5-year backtest shows a typical error of ±43.6%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20264.10.0016
20273.60.0016
20283.10.0015
20292.60.0015
20302.20.0015

Brewer's Blackbird Survey Routes in Colorado

Routes recording Brewer's Blackbird in Colorado.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Yampa10420231969
Alamosa5820251988
Pagosa Spgs5619821968
Dolores5519871968
Briggsdale3520081968
Guffey3520251990
Black Sulphur Cr3520252015
Yellowjacket Pass3320251998
Lay3220251996
Castleton3120251988
Buford3020251970
Kiowa2920181969
Dinosaur2820251995
Powderhorn2720251994
Cochetopa Pass2720251998
Colona 22420252015
Cokedale2320251995
Steamboat L.2320251996
Fleming2220252014
Cortez 22220172009
Heeney 22120252025
Tincup2020251992
Lake City1919881988
Moffat1820251970
Blanca1819871979

Brewer's Blackbird Population Trend in Other States

arizonacaliforniaidahoindianamichiganminnesotamontananebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.