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

Brown-headed Cowbird Population Trend in Utah

All statesGeneralists

Brown-headed Cowbird in Utah has increased: up 39% on the route-weighted index since 1970.

+39%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 UtahNotable 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 Utah. See the full index history below.

Brown-headed Cowbird Population Forecast in Utah

If the recent trend holds, Brown-headed Cowbird in Utah is projected to rise about 10% by 2029 — from 2.4 in 2024 to a central estimate of 2.6 (95% range 0.00–9.0). A 5-year backtest shows a typical error of ±53.2%, with 100% of held-out values landing inside the 95% band.

+10%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 →
2.6Projected 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 →
0.00–9.095% 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 →
±53.2%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 Utah is projected to rise about 10% by 2029 — from 2.4 in 2024 to a central estimate of 2.6 (95% range 0.00–9.0). A 5-year backtest shows a typical error of ±53.2%, 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 →
20252.80.009.2
20262.80.009.2
20272.70.009.1
20282.70.009.1
20292.60.009.0

Brown-headed Cowbird Survey Routes in Utah

Routes recording Brown-headed Cowbird in Utah.
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 →
Woodruff2720242002
Newcastle2420221997
Randolph2020241992
Bear River1520231992
Beck1319871969
Johnson Can1320241988
Fish Springs1319871987
Wellington 21220112003
Delta1020241987
Leamington1020161992
Kelton919951993
Hardware Ranch920181998
Wendover819971974
Moquith Mtn820241987
Promontory720241969
Jensen720241992
Hanna720241997
Wellington720021998
Wellington 3620242012
Goose Creek Mtn.620231997
Pine Creek620231998
Castleton519851970
Bonanza520081992
Lost Cr. Res520171995
Hyrum419751975

Brown-headed Cowbird Population Trend in Other States

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

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