BirdAnalyst
Species · BCR 27 · BBS 2026 Release · 1966–2025

Royal Tern In Southeastern Coastal Plain

All regionsSoutheastern Coastal PlainWetland birds

Royal Tern in Southeastern Coastal Plain has fallen sharply: down 72% on the route-weighted index since 1968.

-72%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 →
33Routes 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 →
59YearsYears 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 →

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 →

Royal Tern has fallen sharply in Southeastern Coastal Plain: down 72% on the route-weighted index since 1968.

Royal Tern In Southeastern Coastal Plain Population Forecast

If the recent trend holds, Royal Tern in Southeastern Coastal Plain is projected to rise about 144% by 2030 — from 0.14 in 2025 to a central estimate of 0.34 (95% range 0.00–0.83). A 5-year backtest shows a typical error of ±163%, with 100% of held-out values landing inside the 95% band.

+144%Change 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 →
0.34Projected 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 →
0.00–0.8395% 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 →
±163%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, Royal Tern in Southeastern Coastal Plain is projected to rise about 144% by 2030 — from 0.14 in 2025 to a central estimate of 0.34 (95% range 0.00–0.83). A 5-year backtest shows a typical error of ±163%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20260.350.000.84
20270.340.000.84
20280.340.000.84
20290.340.000.83
20300.340.000.83

Routes In Southeastern Coastal Plain

Routes recording Royal 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 Is 3ALABAMA262021
Alligator PtFLORIDA182022
Myrtle GroveNORTH-CAROLINA172025
Dauphin IsALABAMA91990
Alabama PtALABAMA62003
Chacaloochee BayALABAMA62019
Dauphin Is 2ALABAMA52019
Milltail CrNORTH-CAROLINA52025
SteinhatcheeFLORIDA31974
Santa RosaFLORIDA32003
SurryVIRGINIA32021
Alabama Pt 2ALABAMA22019
Ft Waltn BchFLORIDA22008
Cross CityFLORIDA22015
Doctors Inlet 2FLORIDA22017
St Vincent IFLORIDA22017
DarienGEORGIA22014
ShallotteNORTH-CAROLINA21990
MashoesNORTH-CAROLINA21982
Johns IsleSOUTH-CAROLINA21979
St. ElmoALABAMA12001
Port St JoeFLORIDA12013
Ft GadsdenFLORIDA11980
Port St Joe 2FLORIDA12019
KellerGEORGIA11988

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.