BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Lesser Scaup

AnatidaeWaterfowlAythya affinis

Lesser Scaup has surged: up 823% on the route-weighted index since 1968.

+823%Since 1968TrendPercent 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 →
321RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Lesser Scaup

The Lesser Scaup (Aythya affinis) is a North American member of the Ducks, Geese & Waterfowl (Anatidae). In this analysis it is grouped with the waterfowl.

Size
12–43.5 in long (30–110 cm) — a medium to large waterfowl (typical for the family)
Habitat
Lakes, ponds, rivers, marshes and sheltered coastal waters.
Diet
Aquatic plants, seeds and invertebrates, dabbled at the surface or dived for.
Range
Recorded on 321 Breeding Bird Survey routes across 19 states, most concentrated in the Prairie Potholes.
Family
Anatidae · Waterfowl

Notable Lesser Scaup TrendsNotable 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 Lesser Scaup. See the full index history below.

Lesser Scaup Population Forecast

If the recent trend holds, Lesser Scaup is projected to rise about 88% by 2029 — from 0.14 in 2024 to a central estimate of 0.27 (95% range 0.11–0.43). A 5-year backtest shows a typical error of ±98.5%, with 40% of held-out values landing inside the 95% band.

+88%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 →
0.27Projected 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 →
0.11–0.4395% 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 →
±98.5%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, Lesser Scaup is projected to rise about 88% by 2029 — from 0.14 in 2024 to a central estimate of 0.27 (95% range 0.11–0.43). A 5-year backtest shows a typical error of ±98.5%, with 40% of held-out values landing inside the 95% band.19662029
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 →
20250.260.090.42
20260.260.100.43
20270.270.100.43
20280.270.100.43
20290.270.110.43

Where the Lesser Scaup Is Detected

BBS routes recording Lesser Scaup, sized by most recent count.

Lesser Scaup Population Trend by State

Lesser Scaup population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alaska+153%198541
California+24%19749
Colorado+568%198918
Idaho+43%197321
Iowainsufficient datan/a2
Kansasinsufficient datan/a1
Michiganinsufficient datan/a1
Minnesota-85%197313
Montana-24%197550
Nebraskainsufficient datan/a3
Nevada-33%19918
New Mexicoinsufficient datan/a3
North Dakota+927%197036
Oregon+170%197120
South Dakota-21%196923
Utah-47%198813
Washington-60%198115
Wisconsininsufficient datan/a6
Wyoming+121%197738

Lesser Scaup Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Lesser Scaup population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
BCR 4-44%198628
Great Basin+183%197161
Northern Rockies+82%197758
Prairie Potholes+476%196969
Southern Rockies / Colorado Plateau+369%198229
Badlands and Prairies+23%197137
Prairie Hardwood Transition-76%19688

Lesser Scaup Conservation Status

Our route-weighted index shows it up about 823% since 1968.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.