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Species · New Hampshire · BBS 2025 Release · 1966–2024

Great Black-backed Gull Population Trend in New Hampshire

All statesWetland birds

Great Black-backed Gull in New Hampshire has collapsed: down 81% on the route-weighted index since 1969.

-81%Since 1969TrendPercent 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 →
5Routes 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 →
23YearsYears 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 New HampshireNotable 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 collapsed in New Hampshire: down 81% on the route-weighted index since 1969.

Great Black-backed Gull Population Forecast in New Hampshire

If the recent trend holds, Great Black-backed Gull in New Hampshire is projected to stay roughly flat through 2010, near 0.00 (95% range 0.00–0.44). A 5-year backtest shows a typical error of ±55.1%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2010TrendPercent 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 2010 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.4495% 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 →
±55.1%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 New Hampshire is projected to stay roughly flat through 2010, near 0.00 (95% range 0.00–0.44). A 5-year backtest shows a typical error of ±55.1%, with 100% of held-out values landing inside the 95% band.19672010
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 →
20060.000.000.44
20070.000.000.44
20080.000.000.44
20090.000.000.44
20100.000.000.44

Great Black-backed Gull Survey Routes in New Hampshire

Routes recording Great Black-backed Gull in New Hampshire.
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 →
Brentwood319831968
Epsom319891985
Dover119981967
Strafford120051969
Jefferson Hl119931993

Great Black-backed Gull Population Trend in Other States

connecticutdelawaremainemarylandmassachusettsnew-jerseynew-yorknorth-carolinaohiorhode-islandvermontvirginia

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