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Species · Alabama · BBS 2025 Release · 1966–2024

Gull-billed Tern Population Trend in Alabama

All statesWetland birds

Gull-billed Tern in Alabama has collapsed: down 94% on the route-weighted index since 1985.

-94%Since 1985TrendPercent 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 →
4Routes 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 →
23YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Gull-billed Tern Trends in AlabamaNotable 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 →

Gull-billed Tern has collapsed in Alabama: down 94% on the route-weighted index since 1985.

Gull-billed Tern Population Forecast in Alabama

If the recent trend holds, Gull-billed Tern in Alabama is projected to stay roughly flat through 2023, near 0.00 (95% range 0.00–0.26). A 5-year backtest shows a typical error of ±642.6%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2023TrendPercent 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 2023 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.2695% 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 →
±642.6%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, Gull-billed Tern in Alabama is projected to stay roughly flat through 2023, near 0.00 (95% range 0.00–0.26). A 5-year backtest shows a typical error of ±642.6%, with 100% of held-out values landing inside the 95% band.19812023
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 →
20190.000.000.26
20200.000.000.26
20210.000.000.26
20220.000.000.26
20230.000.000.26

Gull-billed Tern Survey Routes in Alabama

Routes recording Gull-billed Tern in Alabama.
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 →
Dauphin Is1119901981
Bon Secour319951995
Alabama Pt219921992
Dauphin Is 2120181991

Gull-billed Tern Population Trend in Other States

californiadelawarefloridageorgialouisianamarylandmississippinorth-carolinasouth-carolinatexasvirginia

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