BirdAnalyst
Species · Montana · BBS 2026 Release · 1966–2025

Brown-headed Cowbird Population Trend in Montana

All statesGeneralists

Brown-headed Cowbird in Montana has surged: up 288% on the route-weighted index since 1970.

+288%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 →
116Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brown-headed Cowbird Trends in MontanaNotable 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 →

Brown-headed Cowbird has surged in Montana: up 288% on the route-weighted index since 1970.

Brown-headed Cowbird Population Forecast in Montana

If the recent trend holds, Brown-headed Cowbird in Montana is projected to stay roughly flat through 2030, near 21 (95% range 15–26). A 5-year backtest shows a typical error of ±20.9%, with 80% of held-out values landing inside the 95% band.

+7%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 →
21Projected 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 →
15–2695% 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 →
±20.9%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 Montana is projected to stay roughly flat through 2030, near 21 (95% range 15–26). A 5-year backtest shows a typical error of ±20.9%, with 80% of held-out values landing inside the 95% band.19682030
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 →
2026201426
2027201526
2028201526
2029211526
2030211526

Brown-headed Cowbird Survey Routes in Montana

Routes recording Brown-headed Cowbird in Montana.
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 →
Albion12120251982
Jordan South9020252016
Glentana7420252015
Lambert7120252021
Glasgow6820251968
Webster5920251978
Powderville5920251968
Pablo Res.5620251995
Winifred5520232023
Lindsay5520242015
Redstone5420251968
Cabin Creek5420252018
Westby5120252015
Oswego4920251978
Reed Point4820251977
Flatwillow4720081968
Dinosaurs H.M.4420252018
Chinook4020252015
Roy3920251988
Ingomar3620251977
Brandenberg3620251968
Ester Lake3620252015
Miles City3520252015
Custer3320222019
Circle3020231970

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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