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Species · Louisiana · BBS 2025 Release · 1966–2024

Forster's Tern Population Trend in Louisiana

All statesWetland birds

Forster's Tern in Louisiana has collapsed: down 86% on the route-weighted index since 1973.

-86%Since 1973TrendPercent 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 →
20Routes 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 →
43YearsYears 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 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 →

Forster's Tern has collapsed in Louisiana: down 86% on the route-weighted index since 1973.

Forster's Tern Population Forecast in Louisiana

If the recent trend holds, Forster's Tern in Louisiana is projected to fall about 100% by 2029 — from 0.27 in 2024 to a central estimate of 0.00 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±63.9%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–1.995% 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 →
±63.9%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 Louisiana is projected to fall about 100% by 2029 — from 0.27 in 2024 to a central estimate of 0.00 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±63.9%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20250.010.001.9
20260.000.001.9
20270.000.001.9
20280.000.001.9
20290.000.001.9

Forster's Tern Survey Routes in Louisiana

Routes recording Forster's 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 →
Creole6119871970
Sabine Nwr1520081989
Sabine Nwr 21420172009
Belair1120131995
Junior1019911987
Woodlawn1020192019
Forked Island1020242008
Grand Isle920182010
Glencoe620142014
Gran Chenier519731970
Carlisle319871987
Hackberry220161976
Mayflower220021995
Forked Island 2220102010
Kaplan219991999
Ltl Chenier 2220112010
Berwick220102000
Lafitte119881988
River Road119971997
Ltl Chenier120241986

Forster's Tern Population Trend in Other States

alabamacaliforniacoloradodelawarefloridageorgiaidahoillinoisindianaiowakansasmarylandmichiganminnesotamontananebraskanevadanew-jerseynew-yorknorth-carolinanorth-dakotaoregonsouth-carolinasouth-dakotatexasutahvirginiawashingtonwisconsinwyoming

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