BirdAnalyst
Species · Colorado · BBS 2025 Release · 1966–2024

Brewer's Blackbird Population Trend in Colorado

All statesGeneralists

Brewer's Blackbird in Colorado has fallen sharply: down 55% on the route-weighted index since 1970.

-55%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 →
142Routes 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 →
56YearsYears 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 55% 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 65% by 2029 — from 6.9 in 2024 to a central estimate of 2.4 (95% range 0.00–15). A 5-year backtest shows a typical error of ±36.1%, with 100% of held-out values landing inside the 95% band.

-65%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 →
2.4Projected 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 →
0.00–1595% 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 →
±36.1%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 65% by 2029 — from 6.9 in 2024 to a central estimate of 2.4 (95% range 0.00–15). A 5-year backtest shows a typical error of ±36.1%, with 100% 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 →
20254.30.0017
20263.90.0016
20273.40.0016
20282.90.0015
20292.40.0015

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
Alamosa5920241988
Pagosa Spgs5619821968
Dolores5519871968
Gribbles Prk4820241994
De Beque4220241992
Briggsdale3520081968
Yellowjacket Pass3320241998
Wilson Creek3020241990
Kiowa2920181969
Paonia2720241992
Cochetopa Pass2720241998
Doyleville2520241988
Mosca2520241992
Falfa2420241971
Castleton2320241988
Powderhorn2320231994
Cortez 22220172009
Deadman Rd.2120241992
Dinosaur2120241995
Animas 22120182005
Buford2020241970
Lake City1919881988
Ludlow1920161999
Blanca1819871979

Brewer's Blackbird Population Trend in Other States

arizonacaliforniaidahoindianamichiganminnesotamontananebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.