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

Ring-billed Gull Population Trend in Colorado

All statesWetland birds

Ring-billed Gull in Colorado has risen sharply: up 59% on the route-weighted index since 1989.

+59%Since 1989TrendPercent 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 →
32Routes 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 Ring-billed 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 →

Ring-billed Gull has risen sharply in Colorado: up 58% on the route-weighted index since 1989.

Ring-billed Gull Population Forecast in Colorado

If the recent trend holds, Ring-billed Gull in Colorado is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.37). A 5-year backtest shows a typical error of ±132.8%, with 100% of held-out values landing inside the 95% band.

+0%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 →
0.05Projected 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 →
0.00–0.3795% 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 →
±132.8%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, Ring-billed Gull in Colorado is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.37). A 5-year backtest shows a typical error of ±132.8%, with 100% of held-out values landing inside the 95% band.19742029
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 →
20250.070.000.38
20260.060.000.38
20270.060.000.37
20280.060.000.37
20290.050.000.37

Ring-billed Gull Survey Routes in Colorado

Routes recording Ring-billed 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 →
Fort Morgan2120001996
Haswell1620101992
Harmony1420231983
Cortez 21220132013
Stillwater Pass1220072000
Briggsdale1120231991
Arsenal719921992
Tarryall420192019
Tincup420191994
Fleming319911991
Walden320241990
Lost Lake320222000
Hudson320041989
Steamboat L.320081997
Wildhorse L220242024
Last Chance119741974
Fruita120012000
Julesburg120142002
Baxter Pass120002000
Alamosa120022002
Como120212021
Antonito120002000
Stillwater Pass 2120102010
Prospect Val119941994
Doyle Bridge119961992

Ring-billed Gull Population Trend in Other States

alabamaarizonacaliforniaconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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