BirdAnalyst
Species · New Hampshire · BBS 2026 Release · 1966–2025

American Bittern Population Trend in New Hampshire

All statesWetland birds

American Bittern in New Hampshire has collapsed: down 75% on the route-weighted index since 1968.

-75%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 →
23Routes 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 →
59YearsYears 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 New HampshireNotable 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 collapsed in New Hampshire: down 75% on the route-weighted index since 1968.

American Bittern Population Forecast in New Hampshire

If the recent trend holds, American Bittern in New Hampshire is projected to stay roughly flat through 2030, near 0.15 (95% range 0.00–0.46). A 5-year backtest shows a typical error of ±80.3%, with 80% of held-out values landing inside the 95% band.

n/aChange by 2030TrendPercent 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 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.4695% 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 →
±80.3%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 New Hampshire is projected to stay roughly flat through 2030, near 0.15 (95% range 0.00–0.46). A 5-year backtest shows a typical error of ±80.3%, with 80% of held-out values landing inside the 95% band.19662030
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 →
20260.170.000.48
20270.160.000.48
20280.160.000.47
20290.150.000.47
20300.150.000.46

American Bittern Survey Routes in New Hampshire

Routes recording American Bittern in New Hampshire.
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 →
Dixvil Notch320171966
Franconia220031966
Peterborough120131969
Brentwood119811968
Fitzwilliam119901969
Dover119861967
Hopkinton120011968
Epsom119921966
Strafford120191967
Canterbury120241967
Gilmantn I W120221969
Wilmot120031972
Mt Chocorua120181976
Walpole120241968
Marlow120241967
Lempster120231973
Crawford Not119731973
Jefferson Hl120212002
Milan120141966
Stratford120221966
Clarksville120171966
East Kingston120072007
Dixville Notch 2120252018

American Bittern Population Trend in Other States

alaskacaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.