BirdAnalyst
Species · New Hampshire · BBS 2025 Release · 1966–2024

American Bittern Population Trend in New Hampshire

All statesWetland birds

American Bittern in New Hampshire has fallen sharply: down 50% on the route-weighted index since 1968.

-50%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 →
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 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 fallen sharply in New Hampshire: down 50% 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 fall about 28% by 2029 — from 0.23 in 2024 to a central estimate of 0.16 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±49.6%, with 80% of held-out values landing inside the 95% band.

-28%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 →
0.16Projected 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 →
0.00–0.4895% 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 →
±49.6%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 fall about 28% by 2029 — from 0.23 in 2024 to a central estimate of 0.16 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±49.6%, with 80% 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 →
20250.180.000.50
20260.180.000.49
20270.170.000.49
20280.170.000.48
20290.160.000.48

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
Dixville Notch 2220242018
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

American Bittern Population Trend in Other States

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

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