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

Cliff Swallow Population Trend in New Hampshire

All statesAerial insectivores

Cliff Swallow in New Hampshire has collapsed: down 93% on the route-weighted index since 1968.

-93%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 →
22Routes 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 Cliff 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 →

Cliff Swallow has collapsed in New Hampshire: down 93% on the route-weighted index since 1968.

Cliff Swallow Population Forecast in New Hampshire

If the recent trend holds, Cliff Swallow in New Hampshire is projected to fall about 100% by 2029 — from 0.32 in 2024 to a central estimate of 0.00 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±364.8%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–3.195% 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 →
±364.8%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, Cliff Swallow in New Hampshire is projected to fall about 100% by 2029 — from 0.32 in 2024 to a central estimate of 0.00 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±364.8%, 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 →
20250.000.003.1
20260.000.003.1
20270.000.003.1
20280.000.003.1
20290.000.003.1

Cliff Swallow Survey Routes in New Hampshire

Routes recording Cliff 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 →
Wilmot819741966
Milan720241966
Peterborough419801968
Gilmantn I W319741971
Crawford Not319751972
Franconia319951969
Brentwood219851985
Fitzwilliam219851966
Marlow219951966
Jefferson Hl220071966
Stratford220061966
Dixvil Notch220051966
Clarksville220221966
Glen220071976
Dover120081966
Hopkinton120071968
Epsom120071976
Concord119711971
Canterbury119771972
Mt Chocorua120061967
Walpole119761972
Lempster119891969

Cliff Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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