BirdAnalyst
Species · BCR 18 · BBS 2026 Release · 1966–2025

Brewer's Sparrow In Shortgrass Prairie

All regionsShortgrass PrairieArid-land birds

Brewer's Sparrow in Shortgrass Prairie has fallen sharply: down 73% on the route-weighted index since 1969.

-73%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 →
45Routes 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 →
58YearsYears 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 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 →

Brewer's Sparrow has fallen sharply in Shortgrass Prairie: down 73% on the route-weighted index since 1969.

Brewer's Sparrow In Shortgrass Prairie Population Forecast

If the recent trend holds, Brewer's Sparrow in Shortgrass Prairie is projected to rise about 13% by 2030 — from 0.29 in 2025 to a central estimate of 0.32 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±17.4%, with 100% 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 →
0.32Projected 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 →
0.00–1.395% 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 →
±17.4%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, Brewer's Sparrow in Shortgrass Prairie is projected to rise about 13% by 2030 — from 0.29 in 2025 to a central estimate of 0.32 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±17.4%, 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 →
20260.350.001.4
20270.350.001.4
20280.340.001.3
20290.330.001.3
20300.320.001.3

Routes In Shortgrass Prairie

Routes recording Brewer's Sparrow in Shortgrass Prairie.
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 →
RockportCOLORADO152024
NunnCOLORADO142025
EdisonCOLORADO102018
ChugwaterWYOMING72024
CrowleyCOLORADO61994
BoyeroCOLORADO52017
KarvalCOLORADO52017
Doyle Bridge 2COLORADO52021
KirkCOLORADO42023
NeegrandeCOLORADO42025
PlainsTEXAS41998
AbarrCOLORADO31998
Last ChanceCOLORADO22015
RushCOLORADO22022
Mica ButteCOLORADO21979
Two ButtesCOLORADO22011
Cone MtnCOLORADO22022
LimonCOLORADO22011
DaltonNEBRASKA21969
KimballNEBRASKA22004
Murray LakeNEBRASKA22011
GrenvilleNEW-MEXICO22010
MaxwellNEW-MEXICO22015
CheyenneWYOMING22025
BriggsdaleCOLORADO12024

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