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

American Bittern Population Trend in Maine

All statesWetland birds

American Bittern in Maine has fallen sharply: down 68% on the route-weighted index since 1969.

-68%Since 1969TrendPercent 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 →
57Routes 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 →
54YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable American Bittern 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 →

American Bittern has fallen sharply in Maine: down 68% on the route-weighted index since 1969.

American Bittern Population Forecast in Maine

If the recent trend holds, American Bittern in Maine is projected to stay roughly flat through 2027, near 0.24 (95% range 0.00–0.52). A 5-year backtest shows a typical error of ±390.7%, with 60% of held-out values landing inside the 95% band.

-1%Change by 2027TrendPercent 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 →
0.24Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5295% 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 →
±390.7%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, American Bittern in Maine is projected to stay roughly flat through 2027, near 0.24 (95% range 0.00–0.52). A 5-year backtest shows a typical error of ±390.7%, with 60% of held-out values landing inside the 95% band.19672027
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 →
20230.240.000.52
20240.240.000.52
20250.240.000.52
20260.240.000.52
20270.240.000.52

American Bittern Survey Routes in Maine

Routes recording American Bittern 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 →
Washburn520051985
Northfield 2419921992
St David420051983
Northfield319801976
Hudson320091973
Pillsbury Pd319681968
Newcastle220071991
Hartford220121976
Manchester219821973
Freedom220221975
Harmony220221968
Topsfield219921992
Eastbrook219851985
Aurora220181988
Moose River219891984
Forest Sta220001967
Boundary220111994
Lake Moxie220092009
Jefferson219961996
Westbrook119901977
Biddeford119781978
Kittery Pt120212021
Wilson Mills120121987
Bethel120132013
Greenwood119721971

American Bittern Population Trend in Other States

alaskacaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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