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

Brown-headed Cowbird Population Trend in Utah

All statesGeneralists

Brown-headed Cowbird in Utah has risen sharply: up 51% on the route-weighted index since 1970.

+51%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 →
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 UtahNotable 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 increasecomputed 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 risen sharply in Utah: up 51% on the route-weighted index since 1970.

Brown-headed Cowbird Population Forecast in Utah

If the recent trend holds, Brown-headed Cowbird in Utah is projected to rise about 18% by 2030 — from 2.2 in 2025 to a central estimate of 2.6 (95% range 0.00–8.9). A 5-year backtest shows a typical error of ±47.5%, with 100% of held-out values landing inside the 95% band.

+18%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 →
2.6Projected 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 →
0.00–8.995% 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 →
±47.5%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 Utah is projected to rise about 18% by 2030 — from 2.2 in 2025 to a central estimate of 2.6 (95% range 0.00–8.9). A 5-year backtest shows a typical error of ±47.5%, 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 →
20262.70.009.1
20272.70.009.0
20282.60.009.0
20292.60.008.9
20302.60.008.9

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 →
Goshen2420251968
Randolph1920251992
Bear River1820251992
Woodruff1520252002
Beck1319871969
Johnson Can1320241988
Fish Springs1319871987
Wellington 21220112003
Jensen1020251992
Leamington1020161992
Kelton919951993
Hardware Ranch920181998
Wendover819971974
Hanna720241997
Wellington720021998
Vernon620251992
Pine Creek620231998
Wellington 3520252012
Castleton519851970
Delta520251987
Bonanza520081992
Moquith Mtn520251987
Lost Cr. Res520171995
Hyrum419751975
Lynn420231983

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 2026-08-14.