BirdAnalyst
Species · BCR 18 · BBS 2025 Release · 1966–2024

Brewer's Sparrow In Shortgrass Prairie

All regionsShortgrass PrairieGeneralists

Brewer's Sparrow in Shortgrass Prairie has fallen sharply: down 72% on the route-weighted index since 1969.

-72%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 →
57YearsYears 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 71% 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 fall about 12% by 2029 — from 0.39 in 2024 to a central estimate of 0.34 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±15.4%, with 100% of held-out values landing inside the 95% band.

-12%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 →
0.34Projected 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 →
0.00–1.495% 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 →
±15.4%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 fall about 12% by 2029 — from 0.39 in 2024 to a central estimate of 0.34 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±15.4%, with 100% 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 →
20250.370.001.4
20260.360.001.4
20270.350.001.4
20280.340.001.4
20290.340.001.4

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
NunnCOLORADO122021
EdisonCOLORADO102018
ChugwaterWYOMING72024
CrowleyCOLORADO61994
BoyeroCOLORADO52017
KarvalCOLORADO52017
Doyle Bridge 2COLORADO52021
Pine BluffWYOMING52021
KirkCOLORADO42023
NeegrandeCOLORADO42024
PlainsTEXAS41998
CheyenneWYOMING42024
AbarrCOLORADO31998
Last ChanceCOLORADO22015
RushCOLORADO22022
Mica ButteCOLORADO21979
Two ButtesCOLORADO22011
Cone MtnCOLORADO22022
LimonCOLORADO22011
DaltonNEBRASKA21969
KimballNEBRASKA22004
Murray LakeNEBRASKA22011
GrenvilleNEW-MEXICO22010
MaxwellNEW-MEXICO22015

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.