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Species · Massachusetts · BBS 2025 Release · 1966–2024

Cliff Swallow Population Trend in Massachusetts

All statesAerial insectivores

Cliff Swallow in Massachusetts has fallen sharply: down 61% on the route-weighted index since 1969.

-61%Since 1969TrendPercent 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 →
15Routes 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 →
38YearsYears 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 MassachusettsNotable 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 fallen sharply in Massachusetts: down 61% on the route-weighted index since 1969.

Cliff Swallow Population Forecast in Massachusetts

If the recent trend holds, Cliff Swallow in Massachusetts is projected to fall about 95% by 2029 — from 0.33 in 2024 to a central estimate of 0.01 (95% range 0.00–0.54). A 5-year backtest shows a typical error of ±105.8%, with 100% of held-out values landing inside the 95% band.

-95%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 →
0.01Projected 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 →
0.00–0.5495% 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 →
±105.8%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 Massachusetts is projected to fall about 95% by 2029 — from 0.33 in 2024 to a central estimate of 0.01 (95% range 0.00–0.54). A 5-year backtest shows a typical error of ±105.8%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.040.000.56
20260.030.000.56
20270.030.000.55
20280.020.000.54
20290.010.000.54

Cliff Swallow Survey Routes in Massachusetts

Routes recording Cliff Swallow in Massachusetts.
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 →
E Pepperell519811968
Cummington 2520242015
Cheshire419931970
Maynard219681968
S Barre219941972
N Orange219721969
Princeton119691969
Belchertown119921975
Warren119751969
Cummington119751975
Chesterfield120081967
Pittsfield119971978
Sheffield120131974
Holden119831981
Hancock120002000

Cliff Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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