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

Brown Thrasher Population Trend in Michigan

All statesGeneralists

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

Brown Thrasher Population Forecast in Michigan

If the recent trend holds, Brown Thrasher in Michigan is projected to fall about 72% by 2029 — from 1.4 in 2024 to a central estimate of 0.38 (95% range 0.00–1.8). A 5-year backtest shows a typical error of ±78.3%, with 40% of held-out values landing inside the 95% band.

-72%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 →
0.38Projected 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 →
0.00–1.895% 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 →
±78.3%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 Michigan is projected to fall about 72% by 2029 — from 1.4 in 2024 to a central estimate of 0.38 (95% range 0.00–1.8). A 5-year backtest shows a typical error of ±78.3%, with 40% 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 →
20250.630.002.1
20260.570.002.0
20270.510.001.9
20280.440.001.9
20290.380.001.8

Brown Thrasher Survey Routes in Michigan

Routes recording Brown Thrasher 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 →
Riggsville1020191967
Sand Lake820241978
Harrietta720241990
Bear Lake620241967
Ola520241974
Cohoctah520232021
Irons419891970
Brush Creek420161974
Skeels420151966
Red Oak420221975
Cedar Run419941994
Mayfield420222001
New Buffalo420141992
Maple Grove320231967
New Troy320231971
Big Rapids319901967
Belding320031983
Pickford320241973
Bell Oak320051966
Beaver Lake320111967
Deckerville320241978
Adair319931974
Pleasant Valley 2320242004
Almena320141993
Gooseneck320102008

Brown Thrasher Population Trend in Other States

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

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