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

Brown-headed Cowbird Population Trend in Oregon

All statesGeneralists

Brown-headed Cowbird in Oregon has declined: down 42% on the route-weighted index since 1970.

-42%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 →
139Routes 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 OregonNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Brown-headed Cowbird in Oregon. See the full index history below.

Brown-headed Cowbird Population Forecast in Oregon

If the recent trend holds, Brown-headed Cowbird in Oregon is projected to fall about 36% by 2030 — from 6.0 in 2025 to a central estimate of 3.8 (95% range 0.92–6.7). A 5-year backtest shows a typical error of ±18.6%, with 100% of held-out values landing inside the 95% band.

-36%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 →
3.8Projected 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 →
0.92–6.795% 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 →
±18.6%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 Oregon is projected to fall about 36% by 2030 — from 6.0 in 2025 to a central estimate of 3.8 (95% range 0.92–6.7). A 5-year backtest shows a typical error of ±18.6%, 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 →
20264.21.47.1
20274.11.37.0
20284.01.16.9
20293.91.06.8
20303.80.926.7

Brown-headed Cowbird Survey Routes in Oregon

Routes recording Brown-headed Cowbird in Oregon.
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 →
Sparta4920251971
Modoc Point 23920252024
Chinchalo2020251993
Wallowa1820252025
Buchanan1720251972
Blizzard Gap1720251984
Newbridge1720251993
Bridgeport1620251986
Modoc Point1620181969
Joseph1620251971
Silver Creek1620251984
Princeton1619851973
Glasgow1620251986
Merrill1620221993
Dayton1520251973
Bly 21520252007
Mt Hood1420251972
Fish Lake1320251972
Umatilla1320251988
Zumwalt1320051995
Bly1220011973
Canby1220251993
Mount Vernon1120241986
Lapham Res.1120251991
Madras1120251997

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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