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

Brown Thrasher Population Trend in Iowa

All statesGeneralists

Brown Thrasher in Iowa has fallen sharply: down 57% on the route-weighted index since 1969.

-57%Since 1969
39Routes In State
57Years

Notable Brown Thrasher Trends in Iowa

long arc declinecomputed index

Brown Thrasher has fallen sharply in Iowa: down 56% on the route-weighted index since 1969.

Brown Thrasher Population Forecast in Iowa

If the recent trend holds, Brown Thrasher in Iowa is projected to rise about 21% by 2029 — from 3.7 in 2024 to a central estimate of 4.4 (95% range 2.2–6.7). A 5-year backtest shows a typical error of ±33%, with 100% of held-out values landing inside the 95% band.

+21%Change by 2029
4.4Projected 2029 index
2.2–6.795% range
±33%Backtest error
19672029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected index95% low95% high
20254.82.57.0
20264.72.56.9
20274.62.46.8
20284.52.36.8
20294.42.26.7

Brown Thrasher Survey Routes in Iowa

Routes recording Brown Thrasher in Iowa.
Mt Hamill1820241967
Washta1620141967
Bedford1520181968
College Spgs1420041967
Red Rock1020241968
College Spgs 2920232005
Zearing819951967
Wales720181967
Maquoketa720241967
Davis Corner620241969
Cedar Valley519971967
Panther520241967
Titonka520241968
Pierson420191968
Burchinal420241995
Melrose320241974
West Liberty320241968
Brooklyn320221967
Alice319991967
Scranton320241967
Clare320181967
Sioux City320241968
Rock Valley320191968
Mccallsburg320241996
Exline220241974

Brown Thrasher Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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