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

Black Tern Population Trend in Idaho

All statesWetland birds

Black Tern in Idaho has declined: down 30% on the route-weighted index since 1978.

-30%Since 1978TrendPercent 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 →
3Routes 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 →
22YearsYears 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 IdahoNotable 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 Black Tern in Idaho. See the full index history below.

Black Tern Population Forecast in Idaho

If the recent trend holds, Black Tern in Idaho is projected to fall about 34% by 2027 — from 0.19 in 2022 to a central estimate of 0.13 (95% range 0.00–0.69). A 5-year backtest shows a typical error of ±64.9%, with 80% of held-out values landing inside the 95% band.

-34%Change 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 →
0.13Projected 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 →
0.00–0.6995% 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 →
±64.9%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 Idaho is projected to fall about 34% by 2027 — from 0.19 in 2022 to a central estimate of 0.13 (95% range 0.00–0.69). A 5-year backtest shows a typical error of ±64.9%, with 80% of held-out values landing inside the 95% band.19702027
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 →
20230.160.000.72
20240.150.000.72
20250.140.000.71
20260.140.000.70
20270.130.000.69

Black Tern Survey Routes in Idaho

Routes recording Black Tern in Idaho.
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 →
Naples620221989
Henry619781978
Springfield219731970

Black Tern Population Trend in Other States

californiacoloradoillinoisindianaiowakansasmainemichiganminnesotamissourimontananebraskanevadanew-yorknorth-dakotaohiooregonsouth-dakotatexasutahwashingtonwisconsinwyoming

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