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

Least Tern Population Trend in Louisiana

All statesWetland birds

Least Tern in Louisiana has increased: up 46% on the route-weighted index since 1971.

+46%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 →
15Routes 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 →
37YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Least Tern Trends in LouisianaNotable 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 Least Tern in Louisiana. See the full index history below.

Least Tern Population Forecast in Louisiana

If the recent trend holds, Least Tern in Louisiana is projected to stay roughly flat through 2029, near 0.42 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±258.1%, 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 →
0.42Projected 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 →
0.00–1.795% 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 →
±258.1%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, Least Tern in Louisiana is projected to stay roughly flat through 2029, near 0.42 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±258.1%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.410.001.7
20260.410.001.7
20270.410.001.7
20280.420.001.7
20290.420.001.7

Least Tern Survey Routes in Louisiana

Routes recording Least Tern in Louisiana.
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 →
Grand Isle1120192010
Junior819881987
Creole319781967
Shaw320151992
Belair220021991
Gran Chenier219761967
Sabine Nwr219961993
Baton Rouge220152015
Hackberry220161971
Carlisle119881988
Lafitte119891989
Ltl Chenier120241986
Sabine Nwr 2120152015
Franklinton120152015
Natchez119931993

Least Tern Population Trend in Other States

alabamaarkansascaliforniacoloradodelawarefloridageorgiaillinoiskansaskentuckymainemarylandmassachusettsmississippimissourinebraskanew-jerseynew-yorknorth-carolinaoklahomasouth-carolinatennesseetexasvirginia

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