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

Tree Swallow Population Trend in Maine

All statesAerial insectivores

Tree Swallow in Maine has collapsed: down 87% on the route-weighted index since 1968.

-87%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 →
77Routes 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 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 →

Tree Swallow has collapsed in Maine: down 87% on the route-weighted index since 1968.

Tree Swallow Population Forecast in Maine

If the recent trend holds, Tree Swallow in Maine is projected to fall about 100% by 2029 — from 1.9 in 2024 to a central estimate of 0.00 (95% range 0.00–7.0). A 5-year backtest shows a typical error of ±75.6%, with 100% 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 →
0.00–7.095% 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 →
±75.6%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 Maine is projected to fall about 100% by 2029 — from 1.9 in 2024 to a central estimate of 0.00 (95% range 0.00–7.0). A 5-year backtest shows a typical error of ±75.6%, 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 →
20250.250.007.3
20260.000.007.0
20270.000.007.0
20280.000.007.0
20290.000.007.0

Tree Swallow Survey Routes in Maine

Routes recording Tree Swallow 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 →
Northfield4519811976
Benton4419801971
Manchester3919951971
Waite2419771977
Medway2020181976
Moose River1820081983
St David1420051982
Forest Sta1320001966
Carrabassett1220231983
Boundary1220161993
Otisfield Gr1120151966
Warren1119901973
Carrying Pl1020231979
Charleston1020191975
Brooks920191977
Jefferson920101991
Turner820101972
Hermon720191966
Seboomook Lk720141972
Grnd Lk Strm720001966
Rome720231996
Harmony620241967
Baxter619841977
Cambridge620141967
Washburn620051979

Tree Swallow Population Trend in Other States

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

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