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

Cape May Warbler In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionForest birds

Cape May Warbler in Boreal Hardwood Transition has surged: up 14× on the route-weighted index since 1970.

14×Since 1970TrendPercent 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 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 →

Cape May Warbler has surged in Boreal Hardwood Transition: up 14× on the route-weighted index since 1970.

Cape May Warbler In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Cape May Warbler in Boreal Hardwood Transition is projected to rise about 26% by 2029 — from 0.39 in 2024 to a central estimate of 0.49 (95% range 0.15–0.82). A 5-year backtest shows a typical error of ±33.2%, with 80% of held-out values landing inside the 95% band.

+26%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 →
0.49Projected 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 →
0.15–0.8295% 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 →
±33.2%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, Cape May Warbler in Boreal Hardwood Transition is projected to rise about 26% by 2029 — from 0.39 in 2024 to a central estimate of 0.49 (95% range 0.15–0.82). A 5-year backtest shows a typical error of ±33.2%, with 80% 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 →
20250.460.130.79
20260.470.130.80
20270.470.140.81
20280.480.150.81
20290.490.150.82

Routes In Boreal Hardwood Transition

Routes recording Cape May 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 →
Sawbill CampMINNESOTA102024
LockportMINNESOTA62024
Eagle RiverWISCONSIN62022
Imp LakeMICHIGAN52016
JordanMINNESOTA52023
HermanMICHIGAN42022
IshpemingMICHIGAN42021
CathroMICHIGAN41995
Sherry LakeMINNESOTA42022
BabbittMINNESOTA42017
ShanagoldenWISCONSIN42022
Land O LakesWISCONSIN42016
CohassetMINNESOTA32013
GlendaleMINNESOTA32022
Popple RiverWISCONSIN32024
OntonagonMICHIGAN22018
BerglandMICHIGAN22022
CunardMICHIGAN21994
ShingletonMICHIGAN22023
Isabella 2MICHIGAN22019
MayfieldMICHIGAN22005
Seney NwrMICHIGAN22014
Hart LakeMINNESOTA22024
DebsMINNESOTA22024
Crane LakeMINNESOTA22023

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