BirdAnalyst
Species · BCR 12 · BBS 2025 Release · 1966–2024

Black-throated Blue Warbler In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionForest birds

Black-throated Blue Warbler in Boreal Hardwood Transition has surged: up 944% on the route-weighted index since 1971.

+944%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 →
79Routes 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 →
55YearsYears 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 944% 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 rise about 21% by 2029 — from 0.56 in 2024 to a central estimate of 0.68 (95% range 0.48–0.87). A 5-year backtest shows a typical error of ±19.8%, with 60% of held-out values landing inside the 95% band.

+21%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 →
0.68Projected 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 →
0.48–0.8795% 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 →
±19.8%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, Black-throated Blue Warbler in Boreal Hardwood Transition is projected to rise about 21% by 2029 — from 0.56 in 2024 to a central estimate of 0.68 (95% range 0.48–0.87). A 5-year backtest shows a typical error of ±19.8%, with 60% of held-out values landing inside the 95% band.19672029
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 →
20250.640.440.83
20260.650.450.84
20270.660.460.85
20280.670.470.86
20290.680.480.87

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
Hiawatha NfMICHIGAN82024
SidnawMICHIGAN82024
Scott'S MarshMICHIGAN72010
Cluster LakesMICHIGAN62009
Brocky LakeMICHIGAN42024
Sawbill CampMINNESOTA42022
RacoMICHIGAN32024
Betchler LksMICHIGAN32024
OntonagonMICHIGAN22019
CunardMICHIGAN21986
ShingletonMICHIGAN22023
TahquamenonMICHIGAN22024
EnsignMICHIGAN22009
CromwellMINNESOTA22004
LockportMINNESOTA22024
Sawbill LndgMINNESOTA22024
BemidjiMINNESOTA21980
MinongWISCONSIN21995
MontrealWISCONSIN22023
CrandonWISCONSIN22013
Land O' Lakes 2WISCONSIN22022
FlambeauWISCONSIN22013
BerglandMICHIGAN12022
MareniscoMICHIGAN12018

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