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

Green Heron Population Trend in Maine

All statesWetland birds

Green Heron in Maine 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 →
22Routes 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 →
35YearsYears 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 MaineNotable 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 →

Green Heron has collapsed in Maine: down 77% on the route-weighted index since 1968.

Green Heron Population Forecast in Maine

If the recent trend holds, Green Heron in Maine is projected to fall about 100% by 2028 — from 0.06 in 2023 to a central estimate of 0.00 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±196.2%, with 40% 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 →
0.00–0.1395% 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 →
±196.2%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, Green Heron in Maine is projected to fall about 100% by 2028 — from 0.06 in 2023 to a central estimate of 0.00 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±196.2%, with 40% 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 →
20240.000.000.13
20250.000.000.13
20260.000.000.13
20270.000.000.13
20280.000.000.13

Green Heron Survey Routes in Maine

Routes recording Green Heron in Maine.
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 →
Westbrook219891980
Kittery Pt219851966
Brooks219771977
Charleston219911991
Cambridge220011977
Cape Neddick120231973
Newcastle119931972
Turner119911991
South Arm119751975
Otisfield Gr119861966
Hartford120041975
Bowdoin Ctr119861979
Manchester119821971
East Troy119941994
Harmony119901990
Hermon119811981
Eastbrook119791979
Medway120002000
Forest Sta119681968
Washburn119901979
Cornville120192019
Rome119981998

Green Heron Population Trend in Other States

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

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