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

Herring Gull Population Trend in Delaware

All statesWetland birds

Herring Gull in Delaware has collapsed: down 77% on the route-weighted index since 1968.

-77%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 →
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 →
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 DelawareNotable 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 Delaware: down 77% on the route-weighted index since 1968.

Herring Gull Population Forecast in Delaware

If the recent trend holds, Herring Gull in Delaware is projected to fall about 100% by 2029 — from 0.40 in 2024 to a central estimate of 0.00 (95% range 0.00–10). A 5-year backtest shows a typical error of ±69.2%, 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 →
0.00–1095% 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 →
±69.2%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 Delaware is projected to fall about 100% by 2029 — from 0.40 in 2024 to a central estimate of 0.00 (95% range 0.00–10). A 5-year backtest shows a typical error of ±69.2%, 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 →
20250.000.0010
20260.000.0010
20270.000.0010
20280.000.0010
20290.000.0010

Herring Gull Survey Routes in Delaware

Routes recording Herring Gull in Delaware.
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 →
Mt Pleasant2219901988
Bethany Bch1219901966
Blackbird920091994
Milton519771971
Pepperbox320161999
Harrington220181966
Dover219791966
Holleyville219951981
Pepperbox 2220242017
Wilmington119671967
Lowes Xrds119911966
Georgetown120051997

Herring Gull Population Trend in Other States

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

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