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

Least Bittern Population Trend in Wisconsin

All statesWetland birds

Least Bittern in Wisconsin has edged up: up 17% on the route-weighted index since 1973.

+17%Since 1973TrendPercent 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 →
18Routes 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 →
23YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Least Bittern Trends in WisconsinNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Least Bittern in Wisconsin. See the full index history below.

Least Bittern Population Forecast in Wisconsin

If the recent trend holds, Least Bittern in Wisconsin is projected to stay roughly flat through 2028, near 0.02 (95% range 0.01–0.03). A 5-year backtest shows a typical error of ±30.7%, with 40% of held-out values landing inside the 95% band.

n/aChange by 2028TrendPercent 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 →
0.02Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.01–0.0395% 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 →
±30.7%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, Least Bittern in Wisconsin is projected to stay roughly flat through 2028, near 0.02 (95% range 0.01–0.03). A 5-year backtest shows a typical error of ±30.7%, with 40% of held-out values landing inside the 95% band.19702028
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 →
20240.020.010.03
20250.020.010.03
20260.020.010.03
20270.020.010.03
20280.020.010.03

Least Bittern Survey Routes in Wisconsin

Routes recording Least Bittern in Wisconsin.
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 →
Unity220092009
Rib Lake220232017
Cochrane120102010
Iron River119851985
Mount Horeb119711971
Mather119861973
Hudson120142014
Dresser119701970
Loraine120032003
Omro119831983
Bashaw120062006
Merrill119971997
Stetsonville120192019
River Falls120142014
Buena Vista120002000
Fall River119941990
Briggsville120172017
Beaver Dam120132013

Least Bittern Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianaiowakansaslouisianamarylandmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooregonsouth-carolinasouth-dakotatexasvermontvirginia

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