BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Cassin's Sparrow Population Analysis

PasserellidaeGrassland birdsPeucaea cassinii

Cassin's Sparrow has risen sharply: up 66% on the route-weighted index since 1969.

+66%Since 1969TrendPercent 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 →
394RoutesSurvey 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 Cassin's Sparrow

The Cassin's Sparrow (Peucaea cassinii) 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 394 Breeding Bird Survey routes across 10 states, most concentrated in the Shortgrass Prairie.
Family
Passerellidae · Grassland birds

Notable Cassin'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 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 →

Cassin's Sparrow has risen sharply in surveyed states: up 66% on the route-weighted index since 1969.

Cassin's Sparrow Population Forecast

If the recent trend holds, Cassin's Sparrow is projected to rise about 15% by 2030 — from 1.4 in 2025 to a central estimate of 1.6 (95% range 0.77–2.5). A 5-year backtest shows a typical error of ±31%, with 100% of held-out values landing inside the 95% band.

+15%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 →
1.6Projected 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 →
0.77–2.595% 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 →
±31%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, Cassin's Sparrow is projected to rise about 15% by 2030 — from 1.4 in 2025 to a central estimate of 1.6 (95% range 0.77–2.5). A 5-year backtest shows a typical error of ±31%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20261.60.762.5
20271.60.762.5
20281.60.762.5
20291.60.772.5
20301.60.772.5

Where the Cassin's Sparrow Is Detected

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

Cassin's Sparrow Population Trend by State

Cassin'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 →
Arizona-64%197115
Arkansasinsufficient datan/a1
Californiainsufficient datan/a1
Colorado+263%197059
Kansas-88%197026
Nebraska-65%197611
New Mexico+6%197064
Oklahoma12×196930
Texas-24%1969181
Wyoming+23%20006

Cassin's Sparrow Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Cassin'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 →
Southern Rockies / Colorado Plateau+436%197631
Shortgrass Prairie+17%1969125
Central Mixed Grass Prairie+60%196966
Edwards Plateau+3%197018
Oaks and Prairies+45%196940
Sierra Madre Occidental-79%197115
Chihuahuan Desert-56%196951
Tamaulipan Brushlands-60%196927
Gulf Coastal Prairie-67%197113

Cassin's Sparrow Conservation Status

Our route-weighted index shows it up about 66% since 1969. 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 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.