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

Black-throated Blue Warbler In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionForest birds

Black-throated Blue Warbler in Boreal Hardwood Transition has surged: up 866% on the route-weighted index since 1971.

+866%Since 1971TrendPercent 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 →
81Routes 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 →
56YearsYears 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 increasecomputed 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 →

Black-throated Blue Warbler has surged in Boreal Hardwood Transition: up 866% on the route-weighted index since 1971.

Black-throated Blue Warbler In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Black-throated Blue Warbler in Boreal Hardwood Transition is projected to stay roughly flat through 2030, near 0.69 (95% range 0.50–0.89). A 5-year backtest shows a typical error of ±19.5%, with 60% of held-out values landing inside the 95% band.

-1%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 →
0.69Projected 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 →
0.50–0.8995% 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 →
±19.5%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, Black-throated Blue Warbler in Boreal Hardwood Transition is projected to stay roughly flat through 2030, near 0.69 (95% range 0.50–0.89). A 5-year backtest shows a typical error of ±19.5%, with 60% of held-out values landing inside the 95% band.19672030
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 →
20260.650.460.84
20270.660.470.85
20280.670.480.87
20290.680.490.88
20300.690.500.89

Routes In Boreal Hardwood Transition

Routes recording Black-throated Blue Warbler 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 →
Imp LakeMICHIGAN92019
LockportMINNESOTA82025
Gibbs CityMICHIGAN72025
Scott'S MarshMICHIGAN72010
SidnawMICHIGAN62025
Cluster LakesMICHIGAN62009
Sawbill LndgMINNESOTA62025
TahquamenonMICHIGAN42025
Sawbill CampMINNESOTA42022
Ned LakeMICHIGAN32025
RacoMICHIGAN32024
Hiawatha NfMICHIGAN32025
Popple RiverWISCONSIN32025
CavourWISCONSIN32025
OntonagonMICHIGAN22019
IshpemingMICHIGAN22025
CunardMICHIGAN21986
ShingletonMICHIGAN22023
Betchler LksMICHIGAN22025
EnsignMICHIGAN22009
CromwellMINNESOTA22004
BemidjiMINNESOTA21980
MinongWISCONSIN21995
MontrealWISCONSIN22023
CrandonWISCONSIN22013

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