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

Forster's Tern Population Trend in Oregon

All statesWetland birds

Forster's Tern in Oregon has fallen sharply: down 67% on the route-weighted index since 1971.

-67%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 →
19Routes 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 →
54YearsYears 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 OregonNotable 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 →

Forster's Tern has fallen sharply in Oregon: down 67% on the route-weighted index since 1971.

Forster's Tern Population Forecast in Oregon

If the recent trend holds, Forster's Tern in Oregon is projected to fall about 100% by 2029 — from 0.16 in 2024 to a central estimate of 0.00 (95% range 0.00–0.59). A 5-year backtest shows a typical error of ±210.1%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–0.5995% 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 →
±210.1%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 Oregon is projected to fall about 100% by 2029 — from 0.16 in 2024 to a central estimate of 0.00 (95% range 0.00–0.59). A 5-year backtest shows a typical error of ±210.1%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.000.000.59
20260.000.000.59
20270.000.000.59
20280.000.000.59
20290.000.000.59

Forster's Tern Survey Routes in Oregon

Routes recording Forster's Tern in Oregon.
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 →
Fish Lake1420241980
Princeton1119851972
Lapham Res.1020222006
Malheur Nwr1019921987
Blizzard Gap720231984
Trout Creek720002000
Merrill520131996
Warner Vally420191994
Modoc Point320181970
Dell Spring219801969
Joseph219971997
Harney Lake220231993
Ordnance119761975
Bly119901990
Crane120242024
Catlow Rim120051996
Umatilla120222022
Sheaville120182013
Chinchalo120151993

Forster's Tern Population Trend in Other States

alabamacaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamarylandmichiganminnesotamontananebraskanevadanew-jerseynew-yorknorth-carolinanorth-dakotasouth-carolinasouth-dakotatexasutahvirginiawashingtonwisconsinwyoming

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