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

Northern Waterthrush Population Trend in New Hampshire

All statesForest birds

Northern Waterthrush in New Hampshire has fallen sharply: down 55% on the route-weighted index since 1968.

-55%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 →
26Routes 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 Northern Waterthrush 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 →

Northern Waterthrush has fallen sharply in New Hampshire: down 55% on the route-weighted index since 1968.

Northern Waterthrush Population Forecast in New Hampshire

If the recent trend holds, Northern Waterthrush in New Hampshire is projected to fall about 35% by 2029 — from 0.46 in 2024 to a central estimate of 0.30 (95% range 0.00–0.80). A 5-year backtest shows a typical error of ±57%, with 80% of held-out values landing inside the 95% band.

-35%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 →
0.30Projected 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 →
0.00–0.8095% 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 →
±57%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, Northern Waterthrush in New Hampshire is projected to fall about 35% by 2029 — from 0.46 in 2024 to a central estimate of 0.30 (95% range 0.00–0.80). A 5-year backtest shows a typical error of ±57%, 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 →
20250.340.000.85
20260.330.000.83
20270.320.000.82
20280.310.000.81
20290.300.000.80

Northern Waterthrush Survey Routes in New Hampshire

Routes recording Northern Waterthrush 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 →
Dixville Notch 2520242018
Fitzwilliam320211966
Clarksville320231967
Brentwood219971972
Hopkinton220231966
Canterbury220241973
Gilmantn I W220161970
Wilmot220231966
Crawford Not219751967
Peterborough120231966
Dover120031973
Epsom120121970
Concord120241966
Strafford120171966
Mt Chocorua120241969
Walpole119911966
Marlow120191967
Lempster120171973
Jefferson Hl120181966
Franconia120171966
Milan120141966
Stratford120221966
Dixvil Notch120171966
Glen120011976
East Kingston120212002

Northern Waterthrush Population Trend in Other States

alaskaconnecticutidahomainemarylandmassachusettsmichiganminnesotamontananew-jerseynew-yorknorth-carolinanorth-dakotaohiopennsylvaniarhode-islandvermontvirginiawashingtonwest-virginiawisconsinwyoming

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