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

Western Grebe Population Trend in Colorado

All statesWetland birds

Western Grebe in Colorado has held roughly steady: up 3% on the route-weighted index since 1992.

+3%Since 1992TrendPercent 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 →
21Routes 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 →
33YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Western Grebe 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 →

No notable trend signals for Western Grebe in Colorado. See the full index history below.

Western Grebe Population Forecast in Colorado

If the recent trend holds, Western Grebe in Colorado is projected to rise about 20% by 2029 — from 0.21 in 2024 to a central estimate of 0.25 (95% range 0.03–0.46). A 5-year backtest shows a typical error of ±79.9%, with 100% of held-out values landing inside the 95% band.

+20%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 →
0.25Projected 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 →
0.03–0.4695% 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 →
±79.9%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 →
19902029
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 →
20250.230.010.45
20260.230.010.45
20270.240.020.46
20280.240.020.46
20290.250.030.46

Western Grebe Survey Routes in Colorado

Routes recording Western Grebe 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 →
Guffey1820241993
Neegrande720181996
Cortez 2520172010
Nunn420171995
Stillwater Pass320062006
Walden220161991
Alamosa220142014
Groundhog Rs220121999
San Luis220241995
Harmony120071990
Arsenal120141991
Falfa120142014
Hudson120122007
Wildhorse L120152015
Tarryall120182018
Dinosaur120162016
Julesburg120192002
Thomasville120062006
Gold Hill120012001
Rifle Falls120141998
Cortez120081990

Western Grebe Population Trend in Other States

arizonacaliforniaidahokansasminnesotamontananebraskanevadanew-mexiconorth-dakotaoregonsouth-dakotautahwashingtonwyoming

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