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

Tree Swallow Population Trend in Vermont

All statesAerial insectivores

Tree Swallow in Vermont has fallen sharply: down 68% on the route-weighted index since 1968.

-68%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 →
26Routes 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 VermontNotable 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 →

Tree Swallow has fallen sharply in Vermont: down 68% on the route-weighted index since 1968.

Tree Swallow Population Forecast in Vermont

If the recent trend holds, Tree Swallow in Vermont is projected to fall about 78% by 2030 — from 4.2 in 2025 to a central estimate of 0.92 (95% range 0.00–8.1). A 5-year backtest shows a typical error of ±37.1%, with 100% of held-out values landing inside the 95% band.

-78%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 →
0.92Projected 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 →
0.00–8.195% 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 →
±37.1%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 Vermont is projected to fall about 78% by 2030 — from 4.2 in 2025 to a central estimate of 0.92 (95% range 0.00–8.1). A 5-year backtest shows a typical error of ±37.1%, 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 →
20262.20.009.4
20271.90.009.1
20281.60.008.8
20291.20.008.5
20300.920.008.1

Tree Swallow Survey Routes in Vermont

Routes recording Tree Swallow in Vermont.
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 →
Hinesburg3419941966
Bristol1720251995
Waterville1619801967
Hardwick1320241966
North Pownal1020251966
East Haven820251966
Newbury720041986
Gaysville620191966
Fletcher520251968
Colchester520251986
Grand Isle520251967
S Reading420241966
Shaftsbury420251966
Northfld Fls420251980
Stratton320251966
St Johnsbury320251970
Greensboro320251967
Landgrove220251966
Post Mills220251966
S Wallingfrd220221966
W Rutland220251966
East Calais220251966
Newbury 2220232005
Stowe220231988
Marlboro120241966

Tree Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.