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

Chimney Swift Population Trend in Vermont

All statesAerial insectivores

Chimney Swift in Vermont has collapsed: down 77% on the route-weighted index since 1968.

-77%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 →
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 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 →

Chimney Swift has collapsed in Vermont: down 77% on the route-weighted index since 1968.

Chimney Swift Population Forecast in Vermont

If the recent trend holds, Chimney Swift in Vermont is projected to fall about 42% by 2029 — from 1.1 in 2024 to a central estimate of 0.64 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±38.4%, with 100% of held-out values landing inside the 95% band.

-42%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 →
0.64Projected 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 →
0.00–2.295% 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 →
±38.4%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, Chimney Swift in Vermont is projected to fall about 42% by 2029 — from 1.1 in 2024 to a central estimate of 0.64 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±38.4%, 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 →
20250.880.002.4
20260.820.002.4
20270.760.002.3
20280.700.002.3
20290.640.002.2

Chimney Swift Survey Routes in Vermont

Routes recording Chimney Swift 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 →
Waterville1719801967
Stowe720241991
Marlboro620241966
Northfld Fls620131987
North Pownal520191966
Newbury520041987
Post Mills420221966
Greensboro420241968
Hinesburg419921973
Bristol420091995
Landgrove320221967
Gaysville320191966
Fletcher320221968
Shaftsbury220231966
East Haven220081966
Middlesex220211968
East Calais220231966
Colchester220141986
Newbury 2220082005
Stratton120241966
S Reading120231966
S Wallingfrd120221966
W Rutland120241966
St Johnsbury120191970
Hardwick120241967

Chimney Swift Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvirginiawest-virginiawisconsinwyoming

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