BirdAnalyst
Species · Massachusetts · BBS 2026 Release · 1966–2025

Tree Swallow Population Trend in Massachusetts

All statesAerial insectivores

Tree Swallow in Massachusetts has declined: down 32% on the route-weighted index since 1968.

-32%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 →
59YearsYears 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 stay roughly flat through 2030, near 6.0 (95% range 2.7–9.4). A 5-year backtest shows a typical error of ±21.6%, with 100% of held-out values landing inside the 95% band.

+10%Change by 2030TrendPercent 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 →
6.0Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
2.7–9.495% 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 →
±21.6%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 stay roughly flat through 2030, near 6.0 (95% range 2.7–9.4). A 5-year backtest shows a typical error of ±21.6%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20266.12.79.5
20276.12.79.5
20286.12.79.4
20296.12.79.4
20306.02.79.4

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 →
Warren 21620252010
Cummington 21620252015
Cheshire1419941969
Mansfield1220241968
Cummington1120141968
Brockton1020191967
Belchertown1020251967
S Barre920251968
N. Andover820251995
Princeton719761969
Chesterfield720251968
Monterey720252019
Marion620251966
Pittsfield620161967
E Pepperell519941966
Ware River520221993
Wellfleet420071966
N Oxford420241968
N Orange420241968
Chilmark319831969
Newburyport320221967
Maynard320251967
Cape Cod Ns319991989
Hancock320151997
Warren220091968

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 2026-08-14.