BirdAnalyst
Species · BCR 22 · BBS 2025 Release · 1966–2024

Brown-headed Cowbird In Eastern Tallgrass Prairie

All regionsEastern Tallgrass PrairieGeneralists

Brown-headed Cowbird in Eastern Tallgrass Prairie has risen sharply: up 72% on the route-weighted index since 1968.

+72%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 →
277Routes 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 →
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 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 72% 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 2029, near 23 (95% range 20–27). A 5-year backtest shows a typical error of ±7.2%, with 100% of held-out values landing inside the 95% band.

+4%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 →
23Projected 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 →
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 →
±7.2%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 Eastern Tallgrass Prairie is projected to stay roughly flat through 2029, near 23 (95% range 20–27). A 5-year backtest shows a typical error of ±7.2%, 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 →
2025231927
2026231927
2027231927
2028231927
2029232027

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
BelleviewILLINOIS822024
MilfordMISSOURI662024
ChandlervillILLINOIS652024
FairlandILLINOIS562024
MurdockNEBRASKA532024
FrontenacMINNESOTA502024
Rock ValleyIOWA492024
LyonsNEBRASKA492024
MonticelloILLINOIS482024
SenecaKANSAS482022
College SpgsIOWA472004
PiersonIOWA472019
Ash CreekMINNESOTA472024
MadisonMISSOURI472024
Kahoka2MISSOURI472024
Cedar ValleyIOWA461997
StillwellILLINOIS452024
RensselaerMISSOURI452024
Grape CreekILLINOIS442024
ThrallKANSAS441970
Mill CreekILLINOIS432024
Terre HauteILLINOIS432024
KearneyMISSOURI432024

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