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

Black Tern Population Trend in Wisconsin

All statesWetland birds

Black Tern in Wisconsin has collapsed: down 99% on the route-weighted index since 1968.

-99%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 →
42Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black Tern 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 →

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 →

Black Tern has collapsed in Wisconsin: down 99% on the route-weighted index since 1968.

Black Tern Population Forecast in Wisconsin

If the recent trend holds, Black Tern in Wisconsin is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.56). A 5-year backtest shows a typical error of ±1284.4%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 →
0.00Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5695% 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 →
±1284.4%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, Black Tern in Wisconsin is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.56). A 5-year backtest shows a typical error of ±1284.4%, with 100% of held-out values landing inside the 95% band.19662027
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 →
20230.000.000.56
20240.000.000.56
20250.000.000.56
20260.000.000.56
20270.000.000.56

Black Tern Survey Routes in Wisconsin

Routes recording Black Tern 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 →
Omro720011966
Land O Lakes619811969
Mount Horeb519861968
Bashaw420042004
Princeton419801967
Union Twp320061972
Weyerhauser319811966
Minong219801967
Hudson220031966
Dresser220211966
Loraine220161966
Cumberland219881966
Phillips219691969
Irma219781968
Hollister219671967
Elderon220011966
Oconto Falls220191968
Pardeeville219961983
Grand View119711971
Couderay119801969
Exeland119721968
Gilman120031995
Omro 2120132002
Eagle River119671967
Popple River119921967

Black Tern Population Trend in Other States

californiacoloradoidahoillinoisindianaiowakansasmainemichiganminnesotamissourimontananebraskanevadanew-yorknorth-dakotaohiooregonsouth-dakotatexasutahwashingtonwyoming

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