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

Brown-headed Cowbird In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionGeneralists

Brown-headed Cowbird in Boreal Hardwood Transition has collapsed: down 79% on the route-weighted index since 1968.

-79%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 →
125Routes 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 →

Brown-headed Cowbird has collapsed in Boreal Hardwood Transition: down 79% on the route-weighted index since 1968.

Brown-headed Cowbird In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Brown-headed Cowbird in Boreal Hardwood Transition is projected to fall about 100% by 2030 — from 2.5 in 2025 to a central estimate of 0.00 (95% range 0.00–3.3). A 5-year backtest shows a typical error of ±84%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–3.395% 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 →
±84%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, Brown-headed Cowbird in Boreal Hardwood Transition is projected to fall about 100% by 2030 — from 2.5 in 2025 to a central estimate of 0.00 (95% range 0.00–3.3). A 5-year backtest shows a typical error of ±84%, 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 →
20260.440.003.7
20270.180.003.5
20280.000.003.3
20290.000.003.3
20300.000.003.3

Routes In Boreal Hardwood Transition

Routes recording Brown-headed Cowbird 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 →
BagleyMINNESOTA422006
Traverse CtyMICHIGAN191992
Wigwam BayMINNESOTA192023
IronsMICHIGAN161989
BenaMINNESOTA151977
WausaukeeWISCONSIN152025
Bear LakeMICHIGAN132025
Pine RiverMINNESOTA132024
BashawWISCONSIN132025
BrainerdMINNESOTA112024
BackusMINNESOTA92025
Iron RiverWISCONSIN92025
PhillipsWISCONSIN92025
CunardMICHIGAN72021
Cedar RunMICHIGAN71999
BemidjiMINNESOTA71980
GreenbushMINNESOTA72025
ChaffeyWISCONSIN72025
GilmanWISCONSIN72025
RiggsvilleMICHIGAN62018
Walloon LakeMICHIGAN62004
FredericMICHIGAN62001
Frederic 2MICHIGAN62013
Island LakeMINNESOTA61995
Little ForkMINNESOTA62024

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