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Species · BCR 2 · BBS 2025 Release · 1966–2024

Aleutian Tern In BCR 2

All regionsBCR 2Wetland birds

Aleutian Tern in BCR 2 has fallen sharply: down 73% on the route-weighted index since 1985.

-73%Since 1985TrendPercent 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 →
10Routes 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 →
37YearsYears 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 →

Aleutian Tern has fallen sharply in BCR 2: down 73% on the route-weighted index since 1985.

Aleutian Tern In BCR 2 Population Forecast

If the recent trend holds, Aleutian Tern in BCR 2 is projected to fall about 49% by 2029 — from 2.6 in 2024 to a central estimate of 1.3 (95% range 0.00–7.7). A 5-year backtest shows a typical error of ±352.4%, with 100% of held-out values landing inside the 95% band.

-49%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 →
0.00–7.795% 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 →
±352.4%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, Aleutian Tern in BCR 2 is projected to fall about 49% by 2029 — from 2.6 in 2024 to a central estimate of 1.3 (95% range 0.00–7.7). A 5-year backtest shows a typical error of ±352.4%, with 100% of held-out values landing inside the 95% band.19832029
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 →
20251.50.008.0
20261.50.007.9
20271.40.007.9
20281.40.007.8
20291.30.007.7

Routes In BCR 2

Routes recording Aleutian Tern in BCR 2.
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 →
King SalmonALASKA212024
KodiakALASKA191984
ChiniakALASKA62015
Kotzebue (Short)ALASKA61986
Cape NomeALASKA42019
Cold BayALASKA22024
Kodiak 2ALASKA22019
CouncilALASKA12006
KotzebueALASKA12010
Cold Bay (Short)ALASKA11990

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