BirdAnalyst
Species · BCR 22 · BBS 2026 Release · 1966–2025

Brown-headed Cowbird In Eastern Tallgrass Prairie

All regionsEastern Tallgrass PrairieGeneralists

Brown-headed Cowbird in Eastern Tallgrass Prairie has risen sharply: up 66% on the route-weighted index since 1968.

+66%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 →
278Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Eastern Tallgrass Prairie: up 66% on the route-weighted index since 1968.

Brown-headed Cowbird In Eastern Tallgrass Prairie Population Forecast

If the recent trend holds, Brown-headed Cowbird in Eastern Tallgrass Prairie is projected to stay roughly flat through 2030, near 23 (95% range 20–27). A 5-year backtest shows a typical error of ±5%, with 100% of held-out values landing inside the 95% band.

+5%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 →
23Projected 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 →
20–2795% 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 →
±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 Eastern Tallgrass Prairie is projected to stay roughly flat through 2030, near 23 (95% range 20–27). A 5-year backtest shows a typical error of ±5%, with 100% of held-out values landing inside the 95% band.19662030
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 →
2026231927
2027231927
2028231927
2029231927
2030232027

Routes In Eastern Tallgrass Prairie

Routes recording Brown-headed Cowbird in Eastern Tallgrass Prairie.
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 →
LincolnvilleKANSAS1332024
NorborneMISSOURI982023
BelleviewILLINOIS942025
LucerneMISSOURI892025
MonticelloILLINOIS762025
MurdockNEBRASKA612025
HudsonIOWA552025
Rock ValleyIOWA542025
Gretna 2NEBRASKA532025
HumphreyILLINOIS512025
FairlandILLINOIS512025
River FallsWISCONSIN512025
FrontenacMINNESOTA502024
SenecaKANSAS482022
FairburyILLINOIS472025
College SpgsIOWA472004
MadisonMISSOURI472024
Kahoka2MISSOURI472024
Cedar ValleyIOWA461997
GulfportILLINOIS442025
ThrallKANSAS441970
WayneILLINOIS432025
BudaILLINOIS422023
HumboldtNEBRASKA422025
ChandlervillILLINOIS412025

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.