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

Herring Gull Population Trend in Connecticut

All statesWetland birds

Herring Gull in Connecticut has edged down: down 18% on the route-weighted index since 1971.

-18%Since 1971TrendPercent 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 →
11Routes 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 →
48YearsYears 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 ConnecticutNotable 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 Herring Gull in Connecticut. See the full index history below.

Herring Gull Population Forecast in Connecticut

If the recent trend holds, Herring Gull in Connecticut is projected to fall about 100% by 2029 — from 0.44 in 2024 to a central estimate of 0.00 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±46.5%, 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 →
0.00–2.895% 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 →
±46.5%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 Connecticut is projected to fall about 100% by 2029 — from 0.44 in 2024 to a central estimate of 0.00 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±46.5%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.200.003.1
20260.140.003.0
20270.080.002.9
20280.020.002.9
20290.000.002.8

Herring Gull Survey Routes in Connecticut

Routes recording Herring Gull in Connecticut.
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 →
Mystic620231973
Westbrook420241969
Southington219951995
E Hartland119871987
Uncasville119921977
Willimantic119971988
Greenwich120001969
Danbury120231971
Long Hill119751975
Mid Haddam119961973
New Hartford119821972

Herring Gull Population Trend in Other States

alabamaalaskacaliforniacoloradodelawarefloridaidahoillinoisindianakansaslouisianamainemarylandmassachusettsmichiganminnesotamontananew-hampshirenew-jerseynew-yorknorth-carolinaohiooregonpennsylvaniarhode-islandsouth-carolinatexasvermontvirginiawashingtonwest-virginiawisconsin

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