BirdAnalyst
Species · BCR 37 · BBS 2025 Release · 1966–2024

Royal Tern In Gulf Coastal Prairie

All regionsGulf Coastal PrairieWetland birds

Royal Tern in Gulf Coastal Prairie has surged: up 141% on the route-weighted index since 1976.

+141%Since 1976TrendPercent 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 →
17Routes 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 →
43YearsYears 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 increasecomputed 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 surged in Gulf Coastal Prairie: up 141% on the route-weighted index since 1976.

Royal Tern In Gulf Coastal Prairie Population Forecast

If the recent trend holds, Royal Tern in Gulf Coastal Prairie is projected to fall about 11% by 2029 — from 1.4 in 2024 to a central estimate of 1.3 (95% range 0.19–2.3). A 5-year backtest shows a typical error of ±31.9%, with 80% of held-out values landing inside the 95% band.

-11%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 →
1.3Projected 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 →
0.19–2.395% 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 →
±31.9%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 Gulf Coastal Prairie is projected to fall about 11% by 2029 — from 1.4 in 2024 to a central estimate of 1.3 (95% range 0.19–2.3). A 5-year backtest shows a typical error of ±31.9%, with 80% of held-out values landing inside the 95% band.19712029
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 →
20251.20.092.3
20261.20.122.3
20271.20.142.3
20281.20.162.3
20291.30.192.3

Routes In Gulf Coastal Prairie

Routes recording Royal Tern in Gulf Coastal Prairie.
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 →
Padre Island PaisTEXAS412015
Bayside 3TEXAS142024
Oyster LakeTEXAS112024
VanderbiltTEXAS51975
Gran ChenierLOUISIANA31982
CreoleLOUISIANA31987
Grand IsleLOUISIANA32019
BaysideTEXAS32003
IndianolaTEXAS22024
StowellTEXAS22022
ChinquapinTEXAS22024
L. Atascosa NwrTEXAS22017
JuniorLOUISIANA11991
Forked IslandLOUISIANA12024
Lag AtascosaTEXAS12012
WinnieTEXAS11994
DanburyTEXAS12023

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