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

Tree Swallow Population Trend in New Hampshire

All statesAerial insectivores

Tree Swallow in New Hampshire has fallen sharply: down 74% on the route-weighted index since 1968.

-74%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 →
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 Tree Swallow 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 →

Tree Swallow has fallen sharply in New Hampshire: down 74% on the route-weighted index since 1968.

Tree Swallow Population Forecast in New Hampshire

If the recent trend holds, Tree Swallow in New Hampshire is projected to fall about 48% by 2030 — from 3.4 in 2025 to a central estimate of 1.8 (95% range 0.00–8.0). A 5-year backtest shows a typical error of ±15.4%, with 100% of held-out values landing inside the 95% band.

-48%Change 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 →
1.8Projected 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 →
0.00–8.095% 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 →
±15.4%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, Tree Swallow in New Hampshire is projected to fall about 48% by 2030 — from 3.4 in 2025 to a central estimate of 1.8 (95% range 0.00–8.0). A 5-year backtest shows a typical error of ±15.4%, with 100% 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 →
20262.90.009.2
20272.60.008.9
20282.30.008.6
20292.10.008.3
20301.80.008.0

Tree Swallow Survey Routes in New Hampshire

Routes recording Tree Swallow 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 →
Crawford Not3219751966
Brentwood1119971966
Milan1120251966
Marlow1020251966
Glen1020251975
Walpole920251966
Epsom820251966
Fitzwilliam520251966
Franconia520241966
Dixvil Notch420171966
Peterborough320251966
Strafford320251966
Wilmot320251966
Lempster320241966
Jefferson Hl320251966
Dover220251966
Canterbury220251966
Gilmantn I W220251969
Mt Chocorua220251966
Stratford220221966
Clarksville220221966
Jeffers Ntch220251993
Dixville Notch 2220252018
Hopkinton120241966
Concord120251966

Tree Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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