BirdAnalyst
Species · BCR 16 · BBS 2026 Release · 1966–2025

Brown-headed Cowbird In Southern Rockies / Colorado Plateau

All regionsSouthern Rockies / Colorado PlateauGeneralists

Brown-headed Cowbird in Southern Rockies / Colorado Plateau has risen sharply: up 55% on the route-weighted index since 1970.

+55%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 →
236Routes 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 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 risen sharply in Southern Rockies / Colorado Plateau: up 54% on the route-weighted index since 1970.

Brown-headed Cowbird In Southern Rockies / Colorado Plateau Population Forecast

If the recent trend holds, Brown-headed Cowbird in Southern Rockies / Colorado Plateau is projected to rise about 40% by 2030 — from 2.4 in 2025 to a central estimate of 3.3 (95% range 0.08–6.5). A 5-year backtest shows a typical error of ±69.6%, with 100% of held-out values landing inside the 95% band.

+40%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 →
3.3Projected 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 →
0.08–6.595% 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 →
±69.6%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 Southern Rockies / Colorado Plateau is projected to rise about 40% by 2030 — from 2.4 in 2025 to a central estimate of 3.3 (95% range 0.08–6.5). A 5-year backtest shows a typical error of ±69.6%, 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 →
20263.40.176.6
20273.30.146.5
20283.30.126.5
20293.30.106.5
20303.30.086.5

Routes In Southern Rockies / Colorado Plateau

Routes recording Brown-headed Cowbird in Southern Rockies / Colorado Plateau.
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 →
DoloresCOLORADO261987
Yellowjacket PassCOLORADO262025
Ragged Mtn.COLORADO202019
TarryallCOLORADO192025
AztecNEW-MEXICO181989
Douglas PassCOLORADO172024
Pleasant ViewCOLORADO172021
Pinos CreekCOLORADO151990
CapulinNEW-MEXICO151993
Pagosa SpgsCOLORADO141982
WalsenburgCOLORADO142025
PasturaNEW-MEXICO142016
BeckUTAH131987
YampaCOLORADO122023
FalfaCOLORADO122025
Wellington 2UTAH122011
Deadman Rd.COLORADO112025
FruitaCOLORADO102007
PaoniaCOLORADO102025
JensenUTAH102025
Sybille CynWYOMING102025
The GapARIZONA91976
BufordCOLORADO92025
Claunch 2NEW-MEXICO92025
Fox CreekCOLORADO82025

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