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

Brown-headed Cowbird Population Trend in Arizona

All statesGeneralists

Brown-headed Cowbird in Arizona has fallen sharply: down 56% on the route-weighted index since 1970.

-56%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 →
88Routes 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 ArizonaNotable 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 Arizona: down 56% on the route-weighted index since 1970.

Brown-headed Cowbird Population Forecast in Arizona

If the recent trend holds, Brown-headed Cowbird in Arizona is projected to stay roughly flat through 2029, near 4.7 (95% range 0.00–11). A 5-year backtest shows a typical error of ±31.5%, with 100% of held-out values landing inside the 95% band.

+9%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 →
4.7Projected 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 →
0.00–1195% 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 →
±31.5%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 Arizona is projected to stay roughly flat through 2029, near 4.7 (95% range 0.00–11). A 5-year backtest shows a typical error of ±31.5%, 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 →
20255.00.0012
20265.00.0012
20274.90.0011
20284.80.0011
20294.70.0011

Brown-headed Cowbird Survey Routes in Arizona

Routes recording Brown-headed Cowbird in Arizona.
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 →
Pomerene3020241968
Amado2820231993
Happy Jack1920241977
Bartlett Res1720241993
Ajo1620011968
Cactus Forest1520241991
Patagonia1420241968
Palo Verde1220131992
Dragoon1220091995
Pinetop1120221993
Cutter1120141992
Pisinimo1119931992
Mormon Lake1019741968
Redington1020231993
The Gap919761968
Prescott820221974
Laguna720231968
Williams720181993
Araby720231992
Dateland620241990
Skull Valley620241996
Wickenburg620232017
Peach Spring620241993
House Rock520211968
Hunt520051968

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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