BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Nelson's Sparrow

PasserellidaeWetland birdsAmmospiza nelsoni

Nelson's Sparrow has surged: up 297% on the route-weighted index since 1970.

+297%Since 1970TrendPercent 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 →
53RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
52Years 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 Nelson's Sparrow

The Nelson's Sparrow (Ammospiza nelsoni) is a North American member of the New World Sparrows (Passerellidae). In this analysis it is grouped with the wetland birds.

Size
4.5–7.5 in long (12–19 cm) — a small songbird (typical for the family)
Habitat
Marshes, ponds, lakeshores and other freshwater wetlands.
Diet
Aquatic invertebrates, small fish, frogs and plant matter.
Range
Recorded on 53 Breeding Bird Survey routes across 6 states, most concentrated in the Prairie Potholes.
Family
Passerellidae · Wetland birds

Notable Nelson's Sparrow 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 Nelson's Sparrow. See the full index history below.

Nelson's Sparrow Population Forecast

If the recent trend holds, Nelson's Sparrow is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.01). A 5-year backtest shows a typical error of ±140.4%, with 40% of held-out values landing inside the 95% band.

n/aChange 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 →
0.01Projected 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 →
0.00–0.0195% 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 →
±140.4%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, Nelson's Sparrow is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.01). A 5-year backtest shows a typical error of ±140.4%, with 40% of held-out values landing inside the 95% band.19672029
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 →
20250.010.000.01
20260.010.000.01
20270.010.000.01
20280.010.000.01
20290.010.000.01

Where the Nelson's Sparrow Is Detected

BBS routes recording Nelson's Sparrow, sized by most recent count.

Nelson's Sparrow Population Trend by State

Nelson's Sparrow 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 →
Maineinsufficient datan/a2
Minnesota-36%198110
Montanainsufficient datan/a3
North Dakota+289%197034
South Dakotainsufficient datan/a3
Wyominginsufficient datan/a1

Nelson's Sparrow Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Nelson's Sparrow 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 →
Prairie Potholes+349%197045
Boreal Hardwood Transition+25%20053

Nelson's Sparrow Conservation Status

Our route-weighted index shows it up about 297% since 1970.

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