BirdAnalyst
Species · BCR 34 · BBS 2026 Release · 1966–2025

Brown-headed Cowbird In Sierra Madre Occidental

All regionsSierra Madre OccidentalGeneralists

Brown-headed Cowbird in Sierra Madre Occidental has fallen sharply: down 63% on the route-weighted index since 1970.

-63%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 →
36Routes 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 →
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 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 fallen sharply in Sierra Madre Occidental: down 63% on the route-weighted index since 1970.

Brown-headed Cowbird In Sierra Madre Occidental Population Forecast

If the recent trend holds, Brown-headed Cowbird in Sierra Madre Occidental is projected to fall about 50% by 2030 — from 6.0 in 2025 to a central estimate of 3.0 (95% range 0.00–9.5). A 5-year backtest shows a typical error of ±36.5%, with 100% of held-out values landing inside the 95% band.

-50%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 →
3.0Projected 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 →
0.00–9.595% 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 →
±36.5%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 Sierra Madre Occidental is projected to fall about 50% by 2030 — from 6.0 in 2025 to a central estimate of 3.0 (95% range 0.00–9.5). A 5-year backtest shows a typical error of ±36.5%, with 100% 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 →
20263.70.0010
20273.60.0010
20283.40.009.9
20293.20.009.7
20303.00.009.5

Routes In Sierra Madre Occidental

Routes recording Brown-headed Cowbird in Sierra Madre Occidental.
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 →
Happy JackARIZONA232025
PomereneARIZONA172025
PatagoniaARIZONA152025
Skull Valley 2ARIZONA142025
AmadoARIZONA132025
McnealARIZONA122025
DragoonARIZONA122009
Tonto Vill.ARIZONA112025
PinetopARIZONA112022
CutterARIZONA112014
Mormon LakeARIZONA101974
AlpineARIZONA102025
RedingtonARIZONA72025
Skull ValleyARIZONA62024
Bartlett ResARIZONA62025
SahuaritaARIZONA62025
PrescottARIZONA52025
SunizonaARIZONA51992
WilliamsARIZONA52025
Aztec PeakARIZONA41978
BlueARIZONA41991
Peña BlancaARIZONA42025
Carr MtnARIZONA42025
ReserveNEW-MEXICO42025
MaineARIZONA32022

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