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

Ring-billed Gull Population Trend in Illinois

All statesWetland birds

Ring-billed Gull in Illinois has surged: up 283% on the route-weighted index since 1979.

+283%Since 1979TrendPercent 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 →
46YearsYears 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 IllinoisNotable 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 surged in Illinois: up 283% on the route-weighted index since 1979.

Ring-billed Gull Population Forecast in Illinois

If the recent trend holds, Ring-billed Gull in Illinois is projected to rise about 211% by 2029 — from 0.69 in 2024 to a central estimate of 2.2 (95% range 0.00–4.5). A 5-year backtest shows a typical error of ±139.6%, with 100% of held-out values landing inside the 95% band.

+211%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 →
2.2Projected 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 →
0.00–4.595% 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 →
±139.6%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, Ring-billed Gull in Illinois is projected to rise about 211% by 2029 — from 0.69 in 2024 to a central estimate of 2.2 (95% range 0.00–4.5). A 5-year backtest shows a typical error of ±139.6%, with 100% of held-out values landing inside the 95% band.19772029
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 →
20252.00.004.3
20262.00.004.4
20272.10.004.4
20282.10.004.4
20292.20.004.5

Ring-billed Gull Survey Routes in Illinois

Routes recording Ring-billed Gull in Illinois.
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 →
Itasca5220241986
Terre Haute3320132013
Yorkville820192001
Geneseo619981998
New Lenox520171979
Sherburnvill420231977
Barrington320111985
Seneca220131998
Pawnee219941994
Sheffield219911986
Le Roy220101993
Wayne220191997
Minonk219981998
Clarksdale119881988
Flora119961996

Ring-billed Gull Population Trend in Other States

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

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