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

Swainson's Thrush Population Trend in New Hampshire

All statesForest birds

Swainson's Thrush in New Hampshire has held roughly steady: down 4% on the route-weighted index since 1968.

-4%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 →
14Routes 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 Swainson's Thrush 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 →

No notable trend signals for Swainson's Thrush in New Hampshire. See the full index history below.

Swainson's Thrush Population Forecast in New Hampshire

If the recent trend holds, Swainson's Thrush in New Hampshire is projected to rise about 17% by 2029 — from 2.0 in 2024 to a central estimate of 2.3 (95% range 1.1–3.5). A 5-year backtest shows a typical error of ±28.6%, with 100% of held-out values landing inside the 95% band.

+17%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 →
2.3Projected 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 →
1.1–3.595% 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 →
±28.6%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, Swainson's Thrush in New Hampshire is projected to rise about 17% by 2029 — from 2.0 in 2024 to a central estimate of 2.3 (95% range 1.1–3.5). A 5-year backtest shows a typical error of ±28.6%, 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 →
20252.21.03.4
20262.21.03.4
20272.31.13.4
20282.31.13.5
20292.31.13.5

Swainson's Thrush Survey Routes in New Hampshire

Routes recording Swainson's Thrush 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 Notch1420171966
Dixville Notch 21420242018
Jeffers Ntch1220241993
Mt Chocorua920241966
Clarksville620241966
Crawford Not519751966
Fitzwilliam119721971
Wilmot120141969
Lempster119711971
Jefferson Hl120241966
Franconia120241966
Milan120231966
Stratford120181969
Glen120191978

Swainson's Thrush Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahoillinoismainemarylandmassachusettsmichiganminnesotamontananebraskanevadanew-mexiconew-yorknorth-carolinaoregonpennsylvaniasouth-dakotautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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