BirdAnalyst
Species · Oregon · BBS 2025 Release · 1966–2024

Brown-headed Cowbird Population Trend in Oregon

All statesGeneralists

Brown-headed Cowbird in Oregon has declined: down 48% on the route-weighted index since 1970.

-48%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 →
138Routes 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 →
56YearsYears 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 34% by 2029 — from 5.7 in 2024 to a central estimate of 3.8 (95% range 0.91–6.6). A 5-year backtest shows a typical error of ±18.6%, with 100% of held-out values landing inside the 95% band.

-34%Change by 2029TrendPercent 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 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.91–6.695% 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 34% by 2029 — from 5.7 in 2024 to a central estimate of 3.8 (95% range 0.91–6.6). A 5-year backtest shows a typical error of ±18.6%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20254.21.47.1
20264.11.27.0
20274.01.16.9
20283.91.06.8
20293.80.916.6

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 →
Umatilla11520231988
Salem3220241993
Mt Hood2220241972
Modoc Point 22220242024
Fandango Can2120241979
Sparta2020011971
Nicolai Mtn.2020241993
Buchanan1920241972
Garfield1720231975
Bly 21720242007
Modoc Point1620181969
Princeton1619851973
Merrill1620221993
Silver Creek1420241984
Fish Lake1420241972
Newbridge1420241993
Coquille1420241994
Green1420241994
Adrian1320211984
Sisters1320241997
Zumwalt1320051995
Deschutes1220241968
Bly1220011973
Chinchalo1220241993
Joseph1120241971

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 2026-05-22.