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

Tree Swallow Population Trend in New Hampshire

All statesAerial insectivores

Tree Swallow in New Hampshire has fallen sharply: down 69% on the route-weighted index since 1968.

-69%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 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 69% 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 43% by 2029 — from 3.6 in 2024 to a central estimate of 2.1 (95% range 0.00–8.4). A 5-year backtest shows a typical error of ±23.3%, with 100% of held-out values landing inside the 95% band.

-43%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 →
2.1Projected 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 →
0.00–8.495% 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 →
±23.3%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, Tree Swallow in New Hampshire is projected to fall about 43% by 2029 — from 3.6 in 2024 to a central estimate of 2.1 (95% range 0.00–8.4). A 5-year backtest shows a typical error of ±23.3%, 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 →
20253.20.009.5
20262.90.009.2
20272.60.008.9
20282.30.008.6
20292.10.008.4

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
Walpole1120241966
Jeffers Ntch1020211993
Milan920241966
Glen820241975
Wilmot720241966
Jefferson Hl620241966
Fitzwilliam520241966
Marlow520241966
Franconia520241966
Mt Chocorua420241966
Dixvil Notch420171966
Dixville Notch 2420242018
Peterborough320241966
Concord320241966
Canterbury320241966
Lempster320241966
Stratford220221966
Clarksville220221966
Dover120241966
Hopkinton120241966
Epsom120231966
Strafford120241966
Gilmantn I W120241969

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 2026-05-22.