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

Tree Swallow Population Trend in Massachusetts

All statesAerial insectivores

Tree Swallow in Massachusetts has declined: down 26% on the route-weighted index since 1968.

-26%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 Tree 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 →

No notable trend signals for Tree Swallow in Massachusetts. See the full index history below.

Tree Swallow Population Forecast in Massachusetts

If the recent trend holds, Tree Swallow in Massachusetts is projected to fall about 22% by 2029 — from 7.8 in 2024 to a central estimate of 6.1 (95% range 2.7–9.5). A 5-year backtest shows a typical error of ±26.4%, with 100% of held-out values landing inside the 95% band.

-22%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 →
6.1Projected 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 →
2.7–9.595% 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 →
±26.4%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 Massachusetts is projected to fall about 22% by 2029 — from 7.8 in 2024 to a central estimate of 6.1 (95% range 2.7–9.5). A 5-year backtest shows a typical error of ±26.4%, 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 →
20256.12.79.5
20266.12.79.5
20276.12.79.5
20286.12.79.5
20296.12.79.5

Tree Swallow Survey Routes in Massachusetts

Routes recording Tree 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 →
Cummington 21820242015
N. Andover1720241995
Chesterfield1520241968
Cheshire1419941969
Mansfield1220241968
Marion1120241966
Cummington1120141968
Brockton1020191967
Belchertown1020241967
Warren 2920242010
S Barre820241968
Gay Head820231996
Princeton719761969
Monterey720242019
Pittsfield620161967
Maynard520221967
E Pepperell519941966
Ware River520221993
Wellfleet420071966
N Oxford420241968
N Orange420241968
Chilmark319831969
Newburyport320221967
Cape Cod Ns319991989
Hancock320151997

Tree Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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