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

Black Tern Population Trend in Montana

All statesWetland birds

Black Tern in Montana has fallen sharply: down 71% on the route-weighted index since 1971.

-71%Since 1971TrendPercent 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 →
12Routes 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 →
35YearsYears 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 MontanaNotable 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 fallen sharply in Montana: down 71% on the route-weighted index since 1971.

Black Tern Population Forecast in Montana

If the recent trend holds, Black Tern in Montana is projected to stay roughly flat through 2028, near 0.00 (95% range 0.00–0.41). A 5-year backtest shows a typical error of ±71.3%, with 100% 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 →
0.00Projected 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 →
0.00–0.4195% 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 →
±71.3%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, Black Tern in Montana is projected to stay roughly flat through 2028, near 0.00 (95% range 0.00–0.41). A 5-year backtest shows a typical error of ±71.3%, with 100% of held-out values landing inside the 95% band.19682028
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 →
20240.020.000.43
20250.010.000.42
20260.010.000.42
20270.010.000.42
20280.000.000.41

Black Tern Survey Routes in Montana

Routes recording Black Tern in Montana.
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 →
Kalispell720181970
St Mary320022002
Great Falls320021978
Sunburst219681968
Malta219891979
Pablo Res.220172009
Glen219781978
Westby220232023
Harlem119931980
Arlee119841968
Augusta119851984
Ester Lake120192019

Black Tern Population Trend in Other States

californiacoloradoidahoillinoisindianaiowakansasmainemichiganminnesotamissourinebraskanevadanew-yorknorth-dakotaohiooregonsouth-dakotatexasutahwashingtonwisconsinwyoming

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