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Species · Alaska · BBS 2025 Release · 1966–2024

Arctic Tern Population Trend in Alaska

All statesWetland birds

Arctic Tern in Alaska has fallen sharply: down 61% on the route-weighted index since 1977.

-61%Since 1977TrendPercent 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 →
81Routes 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 →
46YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Arctic Tern Trends in AlaskaNotable 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 →

Arctic Tern has fallen sharply in Alaska: down 61% on the route-weighted index since 1977.

Arctic Tern Population Forecast in Alaska

If the recent trend holds, Arctic Tern in Alaska is projected to rise about 194% by 2029 — from 0.79 in 2024 to a central estimate of 2.3 (95% range 0.00–4.8). A 5-year backtest shows a typical error of ±310.7%, with 40% of held-out values landing inside the 95% band.

+194%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 →
2.3Projected 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 →
0.00–4.895% 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 →
±310.7%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, Arctic Tern in Alaska is projected to rise about 194% by 2029 — from 0.79 in 2024 to a central estimate of 2.3 (95% range 0.00–4.8). A 5-year backtest shows a typical error of ±310.7%, with 40% of held-out values landing inside the 95% band.19752029
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 →
20252.30.004.8
20262.30.004.8
20272.30.004.8
20282.30.004.8
20292.30.004.8

Arctic Tern Survey Routes in Alaska

Routes recording Arctic Tern in Alaska.
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 →
Goodnews Bay6320051999
Kanektok Riv4820051995
Cape Nome3420241993
Togiak River2620051994
Adak1419971984
Nome1120231993
Seven Lakes920231986
Kenny Lake619901990
Cold Bay620242009
Moose Pass519921983
Cold Bay (Short)519911984
Porcupine R.520021993
Sourdough420171989
Tangle Lakes419871987
Mud River420131993
Skagway420241994
Ft. Richrdsn420221996
Seward319841982
Kodiak319831983
Cordova320121983
Cohoe320182013
Mitkof Isle319891989
Kodiak 2320191985
Copper River320111993
Kugarak (Short)319871986

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