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Species · Wyoming · BBS 2025 Release · 1966–2024

Brown-headed Cowbird Population Trend in Wyoming

All statesGeneralists

Brown-headed Cowbird in Wyoming has surged: up 388% on the route-weighted index since 1971.

+388%Since 1971TrendPercent 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 →
130Routes 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 →
55YearsYears 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 WyomingNotable 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 surged in Wyoming: up 388% on the route-weighted index since 1971.

Brown-headed Cowbird Population Forecast in Wyoming

If the recent trend holds, Brown-headed Cowbird in Wyoming is projected to rise about 33% by 2029 — from 4.5 in 2024 to a central estimate of 6.0 (95% range 2.6–9.4). A 5-year backtest shows a typical error of ±61.8%, with 100% of held-out values landing inside the 95% band.

+33%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 →
6.0Projected 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 →
2.6–9.495% 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 →
±61.8%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 Wyoming is projected to rise about 33% by 2029 — from 4.5 in 2024 to a central estimate of 6.0 (95% range 2.6–9.4). A 5-year backtest shows a typical error of ±61.8%, 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 →
20255.82.49.2
20265.82.49.2
20275.92.59.3
20285.92.59.3
20296.02.69.4

Brown-headed Cowbird Survey Routes in Wyoming

Routes recording Brown-headed Cowbird in Wyoming.
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 →
Upton3920241987
Yoder3320241968
Midvale2520221975
Schoonover2520241985
Arvada2520241988
Recluse2320241988
Wyarno2220241975
Shawnee1720241988
Newcastle1620241988
Mayoworth1420241982
Sussex1320241991
Rock River1220221990
Moskee 21120212003
Hayden Val1119861986
Farson1020242001
Seedskadee920231993
Colter Bay 2920242021
Colter Bay819991968
Ethete820241991
Sybille Cyn820241980
Sundance720241975
Fontenelle720241982
Seely720001990
Green River719841984
Harmony720231980

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsin

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