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

Great Black-backed Gull Population Trend in Maine

All statesWetland birds

Great Black-backed Gull in Maine has surged: up 111% on the route-weighted index since 1968.

+111%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 →
17Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Great Black-backed Gull Trends in MaineNotable 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 →

Great Black-backed Gull has surged in Maine: up 111% on the route-weighted index since 1968.

Great Black-backed Gull Population Forecast in Maine

If the recent trend holds, Great Black-backed Gull in Maine is projected to stay roughly flat through 2029, near 0.44 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±106.8%, with 80% of held-out values landing inside the 95% band.

-6%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 →
0.44Projected 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 →
0.00–1.695% 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 →
±106.8%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, Great Black-backed Gull in Maine is projected to stay roughly flat through 2029, near 0.44 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±106.8%, with 80% 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 →
20250.460.001.6
20260.460.001.6
20270.450.001.6
20280.450.001.6
20290.440.001.6

Great Black-backed Gull Survey Routes in Maine

Routes recording Great Black-backed Gull in Maine.
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 →
Kittery Pt920241966
Hartford719881975
Newcastle420071971
Medway319791976
Biddeford219751973
Deblois219981969
Cape Neddick119931975
Westbrook119881977
Turner119961996
Warren119851973
Brooks119931984
St David120052004
Jefferson119961996
Hancock119871969
Castine120001982
Cooper120071977
Moose River119871986

Great Black-backed Gull Population Trend in Other States

connecticutdelawaremarylandmassachusettsnew-hampshirenew-jerseynew-yorknorth-carolinaohiorhode-islandvermontvirginia

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