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

Brown-headed Cowbird Population Trend in Michigan

All statesGeneralists

Brown-headed Cowbird in Michigan has fallen sharply: down 62% on the route-weighted index since 1968.

-62%Since 1968TrendPercent 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 →
58YearsYears 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 MichiganNotable 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 Michigan: down 61% on the route-weighted index since 1968.

Brown-headed Cowbird Population Forecast in Michigan

If the recent trend holds, Brown-headed Cowbird in Michigan is projected to fall about 47% by 2029 — from 7.2 in 2024 to a central estimate of 3.9 (95% range 0.00–7.8). A 5-year backtest shows a typical error of ±35.1%, with 100% of held-out values landing inside the 95% band.

-47%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 →
3.9Projected 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 →
0.00–7.895% 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 →
±35.1%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 Michigan is projected to fall about 47% by 2029 — from 7.2 in 2024 to a central estimate of 3.9 (95% range 0.00–7.8). A 5-year backtest shows a typical error of ±35.1%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20254.60.738.5
20264.40.538.3
20274.20.348.1
20284.00.157.9
20293.90.007.8

Brown-headed Cowbird Survey Routes in Michigan

Routes recording Brown-headed Cowbird in Michigan.
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 →
Richmond3420241999
Hartland3020111992
St Charles2920191967
Bell Oak2920081966
Belding2420031983
Ola2220241974
Lawrence2120241969
Bell Oak 22120232016
Traverse Cty1919921974
Howardsville1920241969
Almena1920151993
Belding 21820242004
Galesburg1720241966
New Buffalo1720141992
Irons1619891970
Bravo1420231974
Coopersville1420241979
Hamburg1420011981
Hamburg 21420242004
Nashville1320241968
No Bradley1320241970
Deckerville1320241978
Monterey1220241978
Remus1220241974
North Branch1219991974

Brown-headed Cowbird Population Trend in Other States

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

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