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

Chestnut-sided Warbler In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionForest birds

Chestnut-sided Warbler in Boreal Hardwood Transition has risen sharply: up 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 →
124Routes 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 →
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 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 →

Chestnut-sided Warbler has risen sharply in Boreal Hardwood Transition: up 74% on the route-weighted index since 1968.

Forecast

If the recent trend holds, Chestnut-sided Warbler in Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 15 (95% range 12–19). A 5-year backtest shows a typical error of ±18.8%, with 60% of held-out values landing inside the 95% band.

-6%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 →
15Projected 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 →
12–1995% 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 →
±18.8%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, Chestnut-sided Warbler in Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 15 (95% range 12–19). A 5-year backtest shows a typical error of ±18.8%, with 60% 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 →
2025151218
2026151219
2027151219
2028151219
2029151219

Routes In Boreal Hardwood Transition

Routes recording Chestnut-sided 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 →
Sherry LakeMINNESOTA642022
ChisholmMINNESOTA622024
Hart LakeMINNESOTA522024
LockportMINNESOTA432024
JordanMINNESOTA402023
Crane LakeMINNESOTA372024
BigforkMINNESOTA372024
Sawbill LndgMINNESOTA362024
Weirgor SpringsWISCONSIN352024
Grand ViewWISCONSIN342024
ConoverWISCONSIN332024
BlackduckMINNESOTA322022
Union TwpWISCONSIN322024
McnaughtonWISCONSIN322024
MinongWISCONSIN312024
MellenWISCONSIN292024
Brocky LakeMICHIGAN282024
IrmaWISCONSIN282024
CouderayWISCONSIN262019
PickfordMICHIGAN252024
BenaMINNESOTA251977
Sawbill CampMINNESOTA252024
Iron RiverWISCONSIN252024
ShanagoldenWISCONSIN252024
Cass LakeMINNESOTA242016

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