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

Brown Thrasher In Eastern Tallgrass Prairie

All regionsEastern Tallgrass PrairieGeneralists

Brown Thrasher in Eastern Tallgrass Prairie has fallen sharply: down 54% on the route-weighted index since 1968.

-54%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 →
276Routes 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 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 Thrasher has fallen sharply in Eastern Tallgrass Prairie: down 54% on the route-weighted index since 1968.

Brown Thrasher In Eastern Tallgrass Prairie Population Forecast

If the recent trend holds, Brown Thrasher in Eastern Tallgrass Prairie is projected to stay roughly flat through 2029, near 3.3 (95% range 1.9–4.8). A 5-year backtest shows a typical error of ±13%, with 100% of held-out values landing inside the 95% band.

-2%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 →
3.3Projected 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 →
1.9–4.895% 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 →
±13%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 Thrasher in Eastern Tallgrass Prairie is projected to stay roughly flat through 2029, near 3.3 (95% range 1.9–4.8). A 5-year backtest shows a typical error of ±13%, 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 →
20253.62.25.1
20263.62.15.0
20273.52.04.9
20283.41.94.8
20293.31.94.8

Routes In Eastern Tallgrass Prairie

Routes recording Brown Thrasher 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 →
Mt HamillIOWA182024
WashtaIOWA162014
BedfordIOWA152018
GrantvilleKANSAS152022
LincolnvilleKANSAS152024
LacledeMISSOURI152024
FloraILLINOIS142022
College SpgsIOWA142004
McfallMISSOURI142024
LucerneMISSOURI142021
BelleviewILLINOIS132024
HuntsvilleMISSOURI132024
NorborneMISSOURI132023
WallaceINDIANA122024
StetMISSOURI121995
TrentonMISSOURI112024
BolckowMISSOURI111992
EmdenMISSOURI112024
MurdockNEBRASKA112024
AthensvilleILLINOIS102024
PaysonILLINOIS102024
Red RockIOWA102024
Trading PostKANSAS102024
HamiltonMISSOURI101985
HumboldtNEBRASKA102024

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