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

Green Heron Population Trend in Maryland

All statesWetland birds

Green Heron in Maryland has declined: down 45% on the route-weighted index since 1968.

-45%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 →
74Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Green Heron 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 →

No notable trend signals for Green Heron in Maryland. See the full index history below.

Green Heron Population Forecast in Maryland

If the recent trend holds, Green Heron in Maryland is projected to fall about 43% by 2029 — from 0.74 in 2024 to a central estimate of 0.42 (95% range 0.04–0.80). A 5-year backtest shows a typical error of ±22.1%, with 100% of held-out values landing inside the 95% band.

-43%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 →
0.42Projected 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 →
0.04–0.8095% 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 →
±22.1%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, Green Heron in Maryland is projected to fall about 43% by 2029 — from 0.74 in 2024 to a central estimate of 0.42 (95% range 0.04–0.80). A 5-year backtest shows a typical error of ±22.1%, 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 →
20250.470.090.85
20260.460.080.84
20270.450.060.83
20280.430.050.82
20290.420.040.80

Green Heron Survey Routes in Maryland

Routes recording Green Heron 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 →
Honga620241966
Indiantown520141977
Olney420241967
Madison420241966
Cokesbury420241966
Grove Neck319961992
Emmitsburg320241966
St. George'S Island320162016
Wheaton320051991
Earlton320192017
Pleasant Val220181966
Jones219921972
Beltsville220081969
Largo219811976
Pt Republic219891972
Piney Neck220231966
Matthews220211970
Sinepuxent219781966
Floyd120001971
Mt Nebo119911969
Vindex120171968
Potomac Park120191970
Williamsport120241969
Smithsburg120101966
Wolfsville120211968

Green Heron Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawashingtonwest-virginiawisconsin

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