BirdAnalyst
Species · BCR 9 · BBS 2026 Release · 1966–2025

Common Merganser In Great Basin

All regionsGreat BasinWaterfowl

Common Merganser in Great Basin has risen sharply: up 71% on the route-weighted index since 1971.

+71%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 →
59Routes 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 →
55YearsYears 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 Great Basin: up 71% on the route-weighted index since 1971.

Common Merganser In Great Basin Population Forecast

If the recent trend holds, Common Merganser in Great Basin is projected to rise about 13% by 2030 — from 0.21 in 2025 to a central estimate of 0.24 (95% range 0.07–0.41). A 5-year backtest shows a typical error of ±85.6%, with 80% of held-out values landing inside the 95% band.

+13%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 →
0.07–0.4195% 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 →
±85.6%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 Great Basin is projected to rise about 13% by 2030 — from 0.21 in 2025 to a central estimate of 0.24 (95% range 0.07–0.41). A 5-year backtest shows a typical error of ±85.6%, with 80% 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 →
20260.230.060.40
20270.230.070.41
20280.240.070.41
20290.240.070.41
20300.240.070.41

Routes In Great Basin

Routes recording Common Merganser in Great Basin.
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 →
Iron GateCALIFORNIA242019
JosephOREGON132024
SistersOREGON112025
Dobbin CreekNEVADA102011
RimrockWASHINGTON82023
FallonNEVADA61998
YakimaWASHINGTON62025
No CascadesWASHINGTON61996
Iron SpringsIDAHO42019
Dougal ResIDAHO42019
NixonNEVADA42023
BrewsterWASHINGTON42015
LeavenworthWASHINGTON41990
Dell SpringOREGON31982
NewhalemWASHINGTON32025
Clear Lk ResCALIFORNIA22004
GiffordIDAHO22017
TriangleIDAHO22024
Magic MtnIDAHO22009
ImnahaOREGON22025
Camp ShermanOREGON21996
AdrianOREGON22008
Bly 2OREGON22011
LynnUTAH22025
TwispWASHINGTON22024

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