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

Forster's Tern Population Trend in Utah

All statesWetland birds

Forster's Tern in Utah has held roughly steady: down 8% on the route-weighted index since 1992.

-8%Since 1992TrendPercent 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 →
8Routes 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 →
34YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Forster's Tern Trends in UtahNotable 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 Forster's Tern in Utah. See the full index history below.

Forster's Tern Population Forecast in Utah

If the recent trend holds, Forster's Tern in Utah is projected to rise about 629% by 2029 — from 0.05 in 2024 to a central estimate of 0.37 (95% range 0.00–1.1). A 5-year backtest shows a typical error of ±310%, with 100% of held-out values landing inside the 95% band.

+629%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 →
0.37Projected 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 →
0.00–1.195% 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 →
±310%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, Forster's Tern in Utah is projected to rise about 629% by 2029 — from 0.05 in 2024 to a central estimate of 0.37 (95% range 0.00–1.1). A 5-year backtest shows a typical error of ±310%, with 100% of held-out values landing inside the 95% band.19862029
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 →
20250.370.001.1
20260.370.001.1
20270.370.001.1
20280.370.001.1
20290.370.001.1

Forster's Tern Survey Routes in Utah

Routes recording Forster's Tern in Utah.
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 →
Bear River3520231992
Neponset Res720181995
Leamington319921992
Randolph320241992
Callao220221992
Promontory119861986
Beck119871987
Saleratus Cr120031998

Forster's Tern Population Trend in Other States

alabamacaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamarylandmichiganminnesotamontananebraskanevadanew-jerseynew-yorknorth-carolinanorth-dakotaoregonsouth-carolinasouth-dakotatexasvirginiawashingtonwisconsinwyoming

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