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

Chimney Swift Population Trend in Maine

All statesAerial insectivores

Chimney Swift in Maine 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 →
73Routes 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 MaineNotable 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 Maine: down 56% on the route-weighted index since 1968.

Chimney Swift Population Forecast in Maine

If the recent trend holds, Chimney Swift in Maine is projected to fall about 100% by 2029 — from 4.2 in 2024 to a central estimate of 0.00 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±106.9%, with 20% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–3.195% 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 →
±106.9%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 Maine is projected to fall about 100% by 2029 — from 4.2 in 2024 to a central estimate of 0.00 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±106.9%, with 20% 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 →
20250.430.003.5
20260.320.003.4
20270.210.003.3
20280.100.003.2
20290.000.003.1

Chimney Swift Survey Routes in Maine

Routes recording Chimney Swift in Maine.
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 →
Kittery Pt5020241966
Otisfield Gr1320151966
Northfield1319791976
Waite1019771977
Aurora920131976
Charleston920191975
Westbrook820241977
Pillsbury Pd819681968
Carrabassett720231983
Hermon620181966
Hudson620161973
Searsport620242003
Turner520101972
Harmony520231967
Hancock520241969
Nesowadnehun519951990
Rome520231997
Warren419901973
Seboomook Lk420141972
Weeks Brook420151996
Brownfield420092009
Bethel320181977
Reeds320241990
Hartford320241975
Castine320001976

Chimney Swift Population Trend in Other States

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

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