BirdAnalyst
Species · BCR 4 · BBS 2025 Release · 1966–2024

Harlequin Duck In BCR 4

All regionsBCR 4Waterfowl

Harlequin Duck in BCR 4 has increased: up 49% on the route-weighted index since 1986.

+49%Since 1986TrendPercent 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 →
31YearsYears 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 →

No notable trend signals for Harlequin Duck in BCR 4. See the full index history below.

Harlequin Duck In BCR 4 Population Forecast

If the recent trend holds, Harlequin Duck in BCR 4 is projected to rise about 98% by 2028 — from 0.16 in 2023 to a central estimate of 0.31 (95% range 0.00–0.78). A 5-year backtest shows a typical error of ±485.4%, with 100% of held-out values landing inside the 95% band.

+98%Change by 2028TrendPercent 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 →
0.31Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.7895% 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 →
±485.4%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, Harlequin Duck in BCR 4 is projected to rise about 98% by 2028 — from 0.16 in 2023 to a central estimate of 0.31 (95% range 0.00–0.78). A 5-year backtest shows a typical error of ±485.4%, with 100% of held-out values landing inside the 95% band.19822028
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 →
20240.310.000.77
20250.310.000.77
20260.310.000.77
20270.310.000.77
20280.310.000.78

Routes In BCR 4

Routes recording Harlequin Duck in BCR 4.
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 →
SourdoughALASKA141994
Unalakleet RiverALASKA62023
SavageALASKA22007
MonahanALASKA11986
CantwellALASKA12018
HomerALASKA11982
Hatcher PassALASKA12007
Kanuti CanynALASKA12014
Anvik RiverALASKA12012
TatalinaALASKA12009

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