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

Royal Tern In Southeastern Coastal Plain

All regionsSoutheastern Coastal PlainWetland birds

Royal Tern in Southeastern Coastal Plain has fallen sharply: down 66% on the route-weighted index since 1968.

-66%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 →
58YearsYears 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 66% 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 160% by 2029 — from 0.14 in 2024 to a central estimate of 0.36 (95% range 0.00–0.85). A 5-year backtest shows a typical error of ±161.9%, with 100% of held-out values landing inside the 95% band.

+160%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 →
0.36Projected 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 →
0.00–0.8595% 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 →
±161.9%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, Royal Tern in Southeastern Coastal Plain is projected to rise about 160% by 2029 — from 0.14 in 2024 to a central estimate of 0.36 (95% range 0.00–0.85). A 5-year backtest shows a typical error of ±161.9%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20250.360.000.86
20260.360.000.86
20270.360.000.86
20280.360.000.85
20290.360.000.85

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
Myrtle GroveNORTH-CAROLINA212024
Alligator PtFLORIDA182022
Dauphin IsALABAMA91990
Alabama PtALABAMA62003
Chacaloochee BayALABAMA62019
Dauphin Is 2ALABAMA52019
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
Kiawah IslandSOUTH-CAROLINA22024
St. ElmoALABAMA12001
Port St JoeFLORIDA12013
Ft GadsdenFLORIDA11980
Port St Joe 2FLORIDA12019
KellerGEORGIA11988

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