BirdAnalyst
Species · Louisiana · BBS 2026 Release · 1966–2025

Least Tern Population Trend in Louisiana

All statesWetland birds

Least Tern in Louisiana has fallen sharply: down 62% on the route-weighted index since 1971.

-62%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 →
38YearsYears 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 →

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 →

Least Tern has fallen sharply in Louisiana: down 62% on the route-weighted index since 1971.

Least Tern Population Forecast in Louisiana

If the recent trend holds, Least Tern in Louisiana is projected to stay roughly flat through 2030, near 0.37 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±650.1%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2030TrendPercent 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 →
0.37Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.695% 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 →
±650.1%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 2030, near 0.37 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±650.1%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20260.370.001.6
20270.370.001.6
20280.370.001.6
20290.370.001.6
20300.370.001.6

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 Chenier120251986
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 2026-08-14.