BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Henslow's Sparrow

PasserellidaeGrassland birdsCentronyx henslowii

Henslow's Sparrow has collapsed: down 82% on the route-weighted index since 1968.

-82%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 →
436RoutesSurvey 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 Henslow's Sparrow

The Henslow's Sparrow (Centronyx henslowii) is a North American member of the New World Sparrows (Passerellidae). In this analysis it is grouped with the grassland birds.

Size
4.5–7.5 in long (12–19 cm) — a small songbird (typical for the family)
Habitat
Open grasslands, prairie, pasture and hayfields.
Diet
Seeds and insects gathered from grasses and the ground.
Range
Recorded on 436 Breeding Bird Survey routes across 22 states, most concentrated in the Eastern Tallgrass Prairie.
Family
Passerellidae · Grassland birds

Notable Henslow'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 →

long arc declinecomputed 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 →

Henslow's Sparrow has collapsed in surveyed states: down 82% on the route-weighted index since 1968.

Henslow's Sparrow Population Forecast

If the recent trend holds, Henslow's Sparrow is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.05). A 5-year backtest shows a typical error of ±49.1%, with 100% 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 →
0.00–0.0595% 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 →
±49.1%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, Henslow's Sparrow is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.05). A 5-year backtest shows a typical error of ±49.1%, with 100% 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 →
20250.010.000.05
20260.010.000.05
20270.010.000.05
20280.010.000.05
20290.010.000.05

Where the Henslow's Sparrow Is Detected

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

Henslow's Sparrow Population Trend by State

Henslow'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 →
Delawareinsufficient datan/a3
Illinois+51%197333
Indiana-73%196832
Iowa+293%197816
Kansas-39%198915
Kentucky+141%197321
Maryland-66%196912
Michigan-95%196836
Minnesota-61%198217
Missouri+370%197440
Nebraskainsufficient datan/a2
New York-82%196842
North Carolina-68%19856
North Dakotainsufficient datan/a2
Ohio-57%196838
Oklahoma-65%19954
Pennsylvania-94%196836
South Dakotainsufficient datan/a2
Vermontinsufficient datan/a2
Virginiainsufficient datan/a3
West Virginia-88%19729
Wisconsin-84%196865

Henslow's Sparrow Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Henslow'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 →
Boreal Hardwood Transition-39%197122
Lower Great Lakes / St. Lawrence Plain-95%196842
Central Mixed Grass Prairie-17%19995
Eastern Tallgrass Prairie+71%1968114
Prairie Hardwood Transition-92%196897
Central Hardwoods-7%196851
Southeastern Coastal Plain-87%19857
Appalachian Mountains-95%196869

Henslow's Sparrow Conservation Status

Our route-weighted index shows it down about 82% since 1968. Grassland birds are North America's steepest-declining group, down roughly 50% since 1970 as prairie and pasture were lost.

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