BirdAnalyst
Species · BCR 27 · BBS 2025 Release · 1966–2024

Gull-billed Tern In Southeastern Coastal Plain

All regionsSoutheastern Coastal PlainWetland birds

Gull-billed Tern in Southeastern Coastal Plain has fallen sharply: down 75% on the route-weighted index since 1968.

-75%Since 1968TrendPercent 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 →
18Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
53YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Gull-billed Tern in Southeastern Coastal Plain. See the full index history below.

Forecast

If the recent trend holds, Gull-billed Tern in Southeastern Coastal Plain is projected to stay roughly flat through 2028, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±82.6%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2028TrendPercent 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 →
0.02Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.1095% 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 →
±82.6%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 Southeastern Coastal Plain is projected to stay roughly flat through 2028, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±82.6%, with 100% of held-out values landing inside the 95% band.19662028
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 →
20240.020.000.11
20250.020.000.11
20260.020.000.11
20270.020.000.10
20280.020.000.10

Routes In Southeastern Coastal Plain

Routes recording Gull-billed Tern in Southeastern Coastal Plain.
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 IsALABAMA111990
Bon SecourALABAMA31995
Alligator PtFLORIDA32017
Port St Joe 2FLORIDA32017
St Vincent IFLORIDA32023
Alabama PtALABAMA21992
Ft Waltn BchFLORIDA21985
Latimer 2MISSISSIPPI22021
MashoesNORTH-CAROLINA21974
ErnulNORTH-CAROLINA22003
Johns IsleSOUTH-CAROLINA21970
Dauphin Is 2ALABAMA12018
Santa RosaFLORIDA11999
DarienGEORGIA12018
MerrimonNORTH-CAROLINA12016
Myrtle GroveNORTH-CAROLINA12017
GrandyNORTH-CAROLINA11971
Kiawah IslandSOUTH-CAROLINA12015

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