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

American Bittern Population Trend in Wisconsin

All statesWetland birds

American Bittern in Wisconsin has declined: down 31% on the route-weighted index since 1968.

-31%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 →
71Routes 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 American 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 American Bittern in Wisconsin. See the full index history below.

American Bittern Population Forecast in Wisconsin

If the recent trend holds, American Bittern in Wisconsin is projected to fall about 22% by 2029 — from 0.07 in 2024 to a central estimate of 0.06 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±25.3%, with 100% of held-out values landing inside the 95% band.

-22%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 →
0.06Projected 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 →
0.00–0.3595% 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 →
±25.3%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, American Bittern in Wisconsin is projected to fall about 22% by 2029 — from 0.07 in 2024 to a central estimate of 0.06 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±25.3%, 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 →
20250.080.000.38
20260.080.000.37
20270.070.000.37
20280.060.000.36
20290.060.000.35

American Bittern Survey Routes in Wisconsin

Routes recording American 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 →
Phillips520221967
Couderay420171969
Holway419831968
Pardeeville419991970
Shanagolden319941977
Elderon320161981
Weirgor Springs320172004
Land O' Lakes 2320222021
Chaffey219921990
Land O Lakes220041979
Rib Lake220171966
Mcnaughton219921967
Mather220231969
Wis Rapids220171969
Omro220001966
Flambeau220081998
Fall River220041970
Cavour220242014
Beaver Dam220041969
Briggsville220192000
Iron River120091985
Minong120181977
Grand View119921992
Bayfield119941967
Montreal119941988

American Bittern Population Trend in Other States

alaskacaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatexasutahvermontvirginiawashingtonwest-virginiawyoming

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