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

Brown-headed Cowbird Population Trend in Washington

All statesGeneralists

Brown-headed Cowbird in Washington has fallen sharply: down 52% on the route-weighted index since 1970.

-52%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 →
108Routes 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 WashingtonNotable 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 Washington: down 52% on the route-weighted index since 1970.

Brown-headed Cowbird Population Forecast in Washington

If the recent trend holds, Brown-headed Cowbird in Washington is projected to stay roughly flat through 2029, near 6.6 (95% range 1.8–11). A 5-year backtest shows a typical error of ±14.8%, with 100% of held-out values landing inside the 95% band.

-8%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 →
6.6Projected 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 →
1.8–1195% 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 →
±14.8%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 Washington is projected to stay roughly flat through 2029, near 6.6 (95% range 1.8–11). A 5-year backtest shows a typical error of ±14.8%, 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 →
20257.02.312
20266.92.212
20276.82.112
20286.72.011
20296.61.811

Brown-headed Cowbird Survey Routes in Washington

Routes recording Brown-headed Cowbird in Washington.
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 →
Othello5219911981
Twisp4920241969
Nighthawk4220241992
Lake Chelan2920241988
Columbia Nwr2920221992
Mesa2720081994
Leavenworth2520241981
Ardenvoir2319871968
Kendall2320241981
Harrington2220121974
Port Angeles2020241970
Wapato1920221979
Scootney Reservoir1920242009
Snowden1820241971
Everett1520241975
Winthrop1420221983
Quincy1320241981
Deer Park1320151994
Index1219711968
Mukilteo1220241993
Hanford Site1219961989
South Elma1120241975
Ellensburg1120241981
Harwood1119971993
Bay View1120171993

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.