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

Great Black-backed Gull Population Trend in Massachusetts

All statesWetland birds

Great Black-backed Gull in Massachusetts has fallen sharply: down 62% on the route-weighted index since 1970.

-62%Since 1970TrendPercent 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 →
12Routes 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 →
53YearsYears 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 MassachusettsNotable 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 →

Great Black-backed Gull has fallen sharply in Massachusetts: down 62% on the route-weighted index since 1970.

Great Black-backed Gull Population Forecast in Massachusetts

If the recent trend holds, Great Black-backed Gull in Massachusetts is projected to fall about 100% by 2028 — from 0.31 in 2023 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.

-100%Change by 2028TrendPercent 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 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.395% 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 →
±85%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 Massachusetts is projected to fall about 100% by 2028 — from 0.31 in 2023 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.19682028
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 →
20240.040.001.3
20250.020.001.3
20260.010.001.3
20270.000.001.3
20280.000.001.3

Great Black-backed Gull Survey Routes in Massachusetts

Routes recording Great Black-backed Gull in Massachusetts.
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 →
Chilmark2219831969
Gay Head420231996
E Pepperell319891989
Marion220111972
Newburyport220221969
Cape Cod Ns220071989
E Dennis120131968
Wellfleet120071970
Prattville119971997
Brockton120192019
Wellfleet 2120212019
N. Andover119951995

Great Black-backed Gull Population Trend in Other States

connecticutdelawaremainemarylandnew-hampshirenew-jerseynew-yorknorth-carolinaohiorhode-islandvermontvirginia

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