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

Great Blue Heron Population Trend in Maine

All statesWetland birds

Great Blue Heron in Maine has declined: down 33% on the route-weighted index since 1968.

-33%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 →
62Routes 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 →
56YearsYears 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 Blue 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 →

No notable trend signals for Great Blue Heron in Maine. See the full index history below.

Great Blue Heron Population Forecast in Maine

If the recent trend holds, Great Blue Heron in Maine is projected to fall about 53% by 2029 — from 0.32 in 2024 to a central estimate of 0.15 (95% range 0.00–0.55). A 5-year backtest shows a typical error of ±44%, with 100% of held-out values landing inside the 95% band.

-53%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 →
0.15Projected 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 →
0.00–0.5595% 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 →
±44%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 Blue Heron in Maine is projected to fall about 53% by 2029 — from 0.32 in 2024 to a central estimate of 0.15 (95% range 0.00–0.55). A 5-year backtest shows a typical error of ±44%, 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 →
20250.180.000.58
20260.170.000.58
20270.160.000.57
20280.150.000.56
20290.150.000.55

Great Blue Heron Survey Routes in Maine

Routes recording Great Blue 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 →
Kittery Pt320231976
Brownfield 2320172013
Greenwood220211972
East Troy220191985
Harmony220171978
Hancock220241969
Deblois220071966
Carrabassett220072000
Seboomook Lk219991999
Cambridge220101976
Wytopitlock219821982
Medway220161976
Pillsbury Pd219681968
Horse Mtn219901983
Ashland219991988
St David219921982
Rome220241998
Cape Neddick120131976
Westbrook120151979
Biddeford120001975
Newcastle120241971
Wilson Mills120231983
Bethel120181979
Turner120021974
Reeds120231983

Great Blue Heron Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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