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

Herring Gull Population Trend in Wisconsin

All statesWetland birds

Herring Gull in Wisconsin has collapsed: down 83% on the route-weighted index since 1968.

-83%Since 1968TrendPercent 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 →
23Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Herring Gull Trends in WisconsinNotable 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 →

Herring Gull has collapsed in Wisconsin: down 83% on the route-weighted index since 1968.

Herring Gull Population Forecast in Wisconsin

If the recent trend holds, Herring Gull in Wisconsin is projected to fall about 100% by 2029 — from 2.6 in 2024 to a central estimate of 0.00 (95% range 0.00–4.7). A 5-year backtest shows a typical error of ±206.2%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–4.795% 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 →
±206.2%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, Herring Gull in Wisconsin is projected to fall about 100% by 2029 — from 2.6 in 2024 to a central estimate of 0.00 (95% range 0.00–4.7). A 5-year backtest shows a typical error of ±206.2%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20250.000.004.7
20260.000.004.7
20270.000.004.7
20280.000.004.7
20290.000.004.7

Herring Gull Survey Routes in Wisconsin

Routes recording Herring Gull in Wisconsin.
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 →
Manitowoc18420241978
Washington I1920241967
Bayfield1319991968
Iron River420241967
Manawa419881988
Montreal219921983
Cochrane220051981
Elderon219821982
Pt Washingtn220171969
Chaffey119881988
Hudson119811981
Dresser119751975
Couderay119821982
Omro 2120212002
Wis Rapids119941994
Oconto Falls119911991
Omro120011968
Casco120241966
Grimms120212004
Brownsville120112011
Rolling Pr119861986
Mount Horeb119841984
Raymond120242004

Herring Gull Population Trend in Other States

alabamaalaskacaliforniacoloradoconnecticutdelawarefloridaidahoillinoisindianakansaslouisianamainemarylandmassachusettsmichiganminnesotamontananew-hampshirenew-jerseynew-yorknorth-carolinaohiooregonpennsylvaniarhode-islandsouth-carolinatexasvermontvirginiawashingtonwest-virginia

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