BirdAnalyst
Species · North Dakota · BBS 2025 Release · 1966–2024

Common Tern Population Trend in North Dakota

All statesWetland birds

Common Tern in North Dakota has surged: up 174% on the route-weighted index since 1979.

+174%Since 1979TrendPercent 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 →
17Routes 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 →
40YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common Tern Trends in North DakotaNotable 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 increasecomputed 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 →

Common Tern has surged in North Dakota: up 173% on the route-weighted index since 1979.

Common Tern Population Forecast in North Dakota

If the recent trend holds, Common Tern in North Dakota is projected to stay roughly flat through 2029, near 0.52 (95% range 0.01–1.0). A 5-year backtest shows a typical error of ±134.3%, with 80% of held-out values landing inside the 95% band.

+9%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 →
0.52Projected 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 →
0.01–1.095% 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 →
±134.3%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, Common Tern in North Dakota is projected to stay roughly flat through 2029, near 0.52 (95% range 0.01–1.0). A 5-year backtest shows a typical error of ±134.3%, with 80% 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 →
20250.490.001.00
20260.500.001.0
20270.510.001.0
20280.510.011.0
20290.520.011.0

Common Tern Survey Routes in North Dakota

Routes recording Common Tern in North Dakota.
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 →
Horsehead Lk1220242001
Emerado819971997
Braddock819891989
Tobacco519791973
Montpelier320222014
Lake George220042004
Douglas Crk220181982
Niles219931993
Danzig120142008
Wild Rose120231985
Powers Lake120241980
Parshall119931984
Buchanan120152004
Sheyenne Lk120091985
Turtle Mtns120041983
Regan119981998
Stanley119921971

Common Tern Population Trend in Other States

alabamaalaskaconnecticutdelawarefloridaidahoindianalouisianamainemarylandmassachusettsmichiganminnesotamontananew-jerseynew-yorknorth-carolinaohiorhode-islandsouth-dakotatexasvermontvirginiawashingtonwisconsinwyoming

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