BirdAnalyst
Species · BCR 12 · BBS 2026 Release · 1966–2025

Tree Swallow In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionAerial insectivores

Tree Swallow in Boreal Hardwood Transition has fallen sharply: down 74% on the route-weighted index since 1968.

-74%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 →
122Routes In RegionSurvey 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 SignalsNotable 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 Boreal Hardwood Transition: down 74% on the route-weighted index since 1968.

Tree Swallow In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Tree Swallow in Boreal Hardwood Transition is projected to stay roughly flat through 2030, near 2.3 (95% range 0.00–6.6). A 5-year backtest shows a typical error of ±28.8%, with 100% of held-out values landing inside the 95% band.

-5%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 →
2.3Projected 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 →
0.00–6.695% 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 →
±28.8%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 Boreal Hardwood Transition is projected to stay roughly flat through 2030, near 2.3 (95% range 0.00–6.6). A 5-year backtest shows a typical error of ±28.8%, 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 →
20263.00.007.4
20272.90.007.2
20282.70.007.0
20292.50.006.8
20302.30.006.6

Routes In Boreal Hardwood Transition

Routes recording Tree Swallow in Boreal Hardwood Transition.
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 →
HerronMICHIGAN402016
Iron RiverWISCONSIN312025
BagleyMINNESOTA272006
FredericMICHIGAN232003
CathroMICHIGAN172016
CunardMICHIGAN162021
Pleasant ValMICHIGAN161997
BrainerdMINNESOTA152024
Cedar RunMICHIGAN141999
Lake CityMICHIGAN132022
Pleasant Valley 2MICHIGAN122025
GilmanWISCONSIN112025
BootjackMICHIGAN102023
RiggsvilleMICHIGAN102019
SkeelsMICHIGAN102015
Wigwam BayMINNESOTA102023
CouderayWISCONSIN102019
PhillipsWISCONSIN102025
FlambeauWISCONSIN102025
Beaver LakeMICHIGAN82011
Frederic 2MICHIGAN82017
Island LakeMINNESOTA81995
BayfieldWISCONSIN82025
HermanMICHIGAN72022
WilsonMICHIGAN72010

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