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

Forster's Tern Population Trend in Virginia

All statesWetland birds

Forster's Tern in Virginia has fallen sharply: down 66% on the route-weighted index since 1970.

-66%Since 1970TrendPercent 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 →
6Routes 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 Forster's Tern Trends in VirginiaNotable 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 Virginia: down 66% on the route-weighted index since 1970.

Forster's Tern Population Forecast in Virginia

If the recent trend holds, Forster's Tern in Virginia is projected to stay roughly flat through 2022, near 0.05 (95% range 0.00–0.14). A 5-year backtest shows a typical error of ±136.3%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2022TrendPercent 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 →
0.05Projected 2022 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.1495% 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 →
±136.3%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, Forster's Tern in Virginia is projected to stay roughly flat through 2022, near 0.05 (95% range 0.00–0.14). A 5-year backtest shows a typical error of ±136.3%, with 100% of held-out values landing inside the 95% band.19662022
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 →
20180.050.000.15
20190.050.000.15
20200.050.000.15
20210.050.000.15
20220.050.000.14

Forster's Tern Survey Routes in Virginia

Routes recording Forster's Tern in Virginia.
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 →
White Stone719961970
Sharps419991999
Quinby319831966
Pungo119941978
Chincoteag W120171995
Cape Charles120131999

Forster's Tern Population Trend in Other States

alabamacaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamarylandmichiganminnesotamontananebraskanevadanew-jerseynew-yorknorth-carolinanorth-dakotaoregonsouth-carolinasouth-dakotatexasutahwashingtonwisconsinwyoming

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