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

Forster's Tern Population Trend in Minnesota

All statesWetland birds

Forster's Tern in Minnesota has increased: up 47% on the route-weighted index since 1975.

+47%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 Forster's Tern Trends in MinnesotaNotable 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 Minnesota. See the full index history below.

Forster's Tern Population Forecast in Minnesota

If the recent trend holds, Forster's Tern in Minnesota is projected to stay roughly flat through 2028, near 0.17 (95% range 0.00–0.53). A 5-year backtest shows a typical error of ±351%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2028TrendPercent 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 →
0.17Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5395% 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 →
±351%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 Minnesota is projected to stay roughly flat through 2028, near 0.17 (95% range 0.00–0.53). A 5-year backtest shows a typical error of ±351%, with 100% of held-out values landing inside the 95% band.19672028
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 →
20240.170.000.53
20250.170.000.53
20260.170.000.53
20270.170.000.53
20280.170.000.53

Forster's Tern Survey Routes in Minnesota

Routes recording Forster's Tern in Minnesota.
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 →
Bagley2020061995
Edwards820221973
Oklee719931993
Le Center520142001
Big Stone320061997
Sherburne Nr219971993
Ash Creek219901990
Gluek219881988
Chokio220041982
Glyndon220232000
Grygla220031980
New London220082008
Tamarac Nwr120191997
Minnetonka119951983
Arlington120041967
Courtland120121981
Redwood Fall119811981
Nebish119921982
Lude119841978
Erie119841984
Badger119981998
Worthington120082008
Tyler119941994
Greenbush119931993

Forster's Tern Population Trend in Other States

alabamacaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamarylandmichiganmontananebraskanevadanew-jerseynew-yorknorth-carolinanorth-dakotaoregonsouth-carolinasouth-dakotatexasutahvirginiawashingtonwisconsinwyoming

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