BirdAnalyst
Species · Massachusetts · BBS 2025 Release · 1966–2024

Chimney Swift Population Trend in Massachusetts

All statesAerial insectivores

Chimney Swift in Massachusetts has fallen sharply: down 56% on the route-weighted index since 1968.

-56%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 →
32Routes 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 Chimney Swift 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 →

Chimney Swift has fallen sharply in Massachusetts: down 56% on the route-weighted index since 1968.

Chimney Swift Population Forecast in Massachusetts

If the recent trend holds, Chimney Swift in Massachusetts is projected to fall about 20% by 2029 — from 5.6 in 2024 to a central estimate of 4.5 (95% range 1.1–7.8). A 5-year backtest shows a typical error of ±20.3%, with 100% of held-out values landing inside the 95% band.

-20%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 →
4.5Projected 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 →
1.1–7.895% 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 →
±20.3%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, Chimney Swift in Massachusetts is projected to fall about 20% by 2029 — from 5.6 in 2024 to a central estimate of 4.5 (95% range 1.1–7.8). A 5-year backtest shows a typical error of ±20.3%, 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 →
20254.81.58.2
20264.71.48.1
20274.61.38.0
20284.61.27.9
20294.51.17.8

Chimney Swift Survey Routes in Massachusetts

Routes recording Chimney Swift 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 Pepperell2719941966
Warren 21920242010
Prattville1820191966
Warren1820091968
N Orange1320241968
Holden1320241977
Mansfield1020241968
Monterey1020242019
Hancock820141997
Wellfleet719971966
Marion620241966
Newburyport620221967
E Dennis520211967
Brockton520191967
Belchertown520241967
Cheshire519931969
Pittsfield520161967
Maynard420221967
S Barre320241968
Gay Head320222017
N Oxford220241968
Chesterfield220241967
Ware River220191994
Chilmark119831969
Littleton120161967

Chimney Swift Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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