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

Caspian Tern Population Trend in Oregon

All statesWetland birds

Caspian Tern in Oregon has edged down: down 11% on the route-weighted index since 1975.

-11%Since 1975TrendPercent 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 →
24Routes 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 →
44YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Caspian 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 →

No notable trend signals for Caspian Tern in Oregon. See the full index history below.

Caspian Tern Population Forecast in Oregon

If the recent trend holds, Caspian Tern in Oregon is projected to stay roughly flat through 2029, near 0.10 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±496.8%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.10Projected 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 →
0.00–0.4295% 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 →
±496.8%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, Caspian Tern in Oregon is projected to stay roughly flat through 2029, near 0.10 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±496.8%, with 100% of held-out values landing inside the 95% band.19712029
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 →
20250.100.000.43
20260.100.000.43
20270.100.000.42
20280.100.000.42
20290.100.000.42

Caspian Tern Survey Routes in Oregon

Routes recording Caspian 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 →
Harney Lake620011993
Glasgow420211989
Wedderburn320041971
Malheur Nwr219971986
Svensen219901990
Umatilla220221988
Monument219931993
Ordnance119751974
Nicolai Mtn.120141993
Fandango Can120162016
Buchanan120022002
Modoc Point120181988
Bly 2120222007
Sparta119961995
Princeton119851981
Hazel Camp120132001
Blizzard Gap120241987
Fish Lake120241984
Merrill120181995
Warner Vally120241994
Catlow Rim120131996
Chinchalo120151995
Lakeview120192019
Trout Creek120002000

Caspian Tern Population Trend in Other States

alabamaalaskacaliforniadelawarefloridaidahoillinoisindianalouisianamarylandmichiganminnesotamontananevadanorth-carolinanorth-dakotasouth-carolinatexasutahvermontvirginiawashingtonwisconsinwyoming

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