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Species · Colorado · BBS 2025 Release · 1966–2024

California Gull Population Trend in Colorado

All statesWetland birds

California Gull in Colorado has surged: up 148× on the route-weighted index since 1986.

148×Since 1986TrendPercent 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 →
15Routes 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 →
40YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable California Gull 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 increasecomputed 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 →

California Gull has surged in Colorado: up 148× on the route-weighted index since 1986.

California Gull Population Forecast in Colorado

If the recent trend holds, California Gull in Colorado is projected to stay roughly flat through 2029, near 9.9 (95% range 3.4–16). A 5-year backtest shows a typical error of ±41.3%, with 60% of held-out values landing inside the 95% band.

-4%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 →
9.9Projected 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 →
3.4–1695% 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 →
±41.3%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, California Gull in Colorado is projected to stay roughly flat through 2029, near 9.9 (95% range 3.4–16). A 5-year backtest shows a typical error of ±41.3%, with 60% of held-out values landing inside the 95% band.19812029
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 →
20258.82.415
20269.12.616
20279.42.916
20289.63.116
20299.93.416

California Gull Survey Routes in Colorado

Routes recording California Gull 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 →
Guffey98220241992
Briggsdale9520231981
Tincup2220111994
Walden920241991
Hudson920241988
Lost Lake420102001
Fort Morgan420002000
Harmony320181992
Julesburg320022002
Tarryall220231990
Yampa120102010
Stillwater Pass120061999
Weston Pass120001995
Como119981998
Doyle Bridge119941992

California Gull Population Trend in Other States

alaskacaliforniaidahominnesotamontananevadanew-mexiconorth-dakotaoregonsouth-dakotautahwashingtonwyoming

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