BirdAnalyst
Species · North Carolina · BBS 2026 Release · 1966–2025

Royal Tern Population Trend in North Carolina

All statesWetland birds

Royal Tern in North Carolina has collapsed: down 80% on the route-weighted index since 1968.

-80%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 →
11Routes 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 →
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 Royal Tern Trends in North CarolinaNotable 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 collapsed in North Carolina: down 80% on the route-weighted index since 1968.

Royal Tern Population Forecast in North Carolina

If the recent trend holds, Royal Tern in North Carolina is projected to fall about 66% by 2030 — from 0.36 in 2025 to a central estimate of 0.12 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±43.4%, with 100% of held-out values landing inside the 95% band.

-66%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 →
0.12Projected 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 →
0.00–1.595% 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 →
±43.4%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 North Carolina is projected to fall about 66% by 2030 — from 0.36 in 2025 to a central estimate of 0.12 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±43.4%, 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 →
20260.220.001.6
20270.200.001.6
20280.170.001.6
20290.150.001.5
20300.120.001.5

Royal Tern Survey Routes in North Carolina

Routes recording Royal Tern in North Carolina.
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 →
Myrtle Grove1720251966
Milltail Cr520251992
Shallotte219901985
Mashoes219821973
Merrimon120221968
Supply120151992
Jarvisburg119991992
Arapahoe119681968
Broad Creek120232023
Newport120231996
Grandy119751971

Royal Tern Population Trend in Other States

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