BirdAnalyst
Species · Alabama · BBS 2025 Release · 1966–2024

Royal Tern Population Trend in Alabama

All statesWetland birds

Royal Tern in Alabama has surged: up 262% on the route-weighted index since 1971.

+262%Since 1971TrendPercent 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 →
7Routes 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 →
48YearsYears 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 AlabamaNotable 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 Alabama: up 262% on the route-weighted index since 1971.

Royal Tern Population Forecast in Alabama

If the recent trend holds, Royal Tern in Alabama is projected to rise about 26% by 2026 — from 0.35 in 2021 to a central estimate of 0.44 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±290.4%, with 100% of held-out values landing inside the 95% band.

+26%Change by 2026TrendPercent 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 →
0.44Projected 2026 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.495% 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 →
±290.4%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 Alabama is projected to rise about 26% by 2026 — from 0.35 in 2021 to a central estimate of 0.44 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±290.4%, with 100% of held-out values landing inside the 95% band.19682026
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 →
20220.430.001.4
20230.430.001.4
20240.440.001.4
20250.440.001.4
20260.440.001.4

Royal Tern Survey Routes in Alabama

Routes recording Royal Tern in Alabama.
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 32620212021
Dauphin Is919901968
Alabama Pt620031968
Chacaloochee Bay620192009
Dauphin Is 2520191991
Alabama Pt 2220192004
St. Elmo120012000

Royal Tern Population Trend in Other States

californiadelawarefloridageorgialouisianamarylandnew-jerseynorth-carolinasouth-carolinatexasvirginia

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