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Species · Maryland · BBS 2025 Release · 1966–2024

Herring Gull Population Trend in Maryland

All statesWetland birds

Herring Gull in Maryland has surged: up 119% on the route-weighted index since 1968.

+119%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 →
21Routes 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 →
52YearsYears 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 MarylandNotable 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 →

Herring Gull has surged in Maryland: up 119% on the route-weighted index since 1968.

Herring Gull Population Forecast in Maryland

If the recent trend holds, Herring Gull in Maryland is projected to rise about 574% by 2028 — from 0.17 in 2023 to a central estimate of 1.2 (95% range 0.00–3.5). A 5-year backtest shows a typical error of ±2011.9%, with 100% of held-out values landing inside the 95% band.

+574%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 →
1.2Projected 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 →
0.00–3.595% 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 →
±2011.9%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 Maryland is projected to rise about 574% by 2028 — from 0.17 in 2023 to a central estimate of 1.2 (95% range 0.00–3.5). A 5-year backtest shows a typical error of ±2011.9%, with 100% of held-out values landing inside the 95% band.19662028
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 →
20241.10.003.4
20251.10.003.4
20261.20.003.4
20271.20.003.4
20281.20.003.5

Herring Gull Survey Routes in Maryland

Routes recording Herring Gull in Maryland.
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 →
Indiantown8120141989
St. George'S Island1320172015
Newark720231967
Mardela620002000
Sinepuxent519751970
Elkton419971969
Golden Hill420211971
Walnut220162004
Melitota219831966
Davidsnville220172017
Pleasant Val119871987
Jones119711970
Berlin120181987
Broomes Isl119711971
Piney Neck119671967
Honga120041968
Madison120181972
Fruitland119941994
Cokesbury120191996
Snow Hill119741974
Severna Park119981998

Herring Gull Population Trend in Other States

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

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