BirdAnalyst
Species · BCR 15 · BBS 2026 Release · 1966–2025

Common Merganser In Sierra Nevada

All regionsSierra NevadaWaterfowl

Common Merganser in Sierra Nevada has risen sharply: up 58% on the route-weighted index since 1972.

+58%Since 1972TrendPercent 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 →
44YearsYears 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 →

Common Merganser has risen sharply in Sierra Nevada: up 58% on the route-weighted index since 1972.

Common Merganser In Sierra Nevada Population Forecast

If the recent trend holds, Common Merganser in Sierra Nevada is projected to stay roughly flat through 2030, near 0.24 (95% range 0.00–0.53). A 5-year backtest shows a typical error of ±97.6%, with 60% of held-out values landing inside the 95% band.

+7%Change by 2030TrendPercent 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 →
0.24Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5395% 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 →
±97.6%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, Common Merganser in Sierra Nevada is projected to stay roughly flat through 2030, near 0.24 (95% range 0.00–0.53). A 5-year backtest shows a typical error of ±97.6%, with 60% of held-out values landing inside the 95% band.19692030
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 →
20260.230.000.53
20270.230.000.53
20280.230.000.53
20290.230.000.53
20300.240.000.53

Routes In Sierra Nevada

Routes recording Common Merganser in Sierra Nevada.
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 →
GeneseeCALIFORNIA62023
RivertonCALIFORNIA42017
Eagle LakeCALIFORNIA32023
ChilcootCALIFORNIA32023
Meadow ValleyCALIFORNIA22025
Little TruckeeCALIFORNIA22017
DardanelleCALIFORNIA12014
Bass LakeCALIFORNIA11981
JohnsvilleCALIFORNIA12021
WoodfordsCALIFORNIA12025
Silver CityCALIFORNIA12013
Tuolumne GroveCALIFORNIA12016
SattleyCALIFORNIA12009
Butte MeadowCALIFORNIA12000
PaxtonCALIFORNIA12025
StrawberryCALIFORNIA12015
Last ChanceCALIFORNIA12009

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.