BirdAnalyst
Species · BCR 10 · BBS 2025 Release · 1966–2024

Brewer's Sparrow In Northern Rockies

All regionsNorthern RockiesGeneralists

Brewer's Sparrow in Northern Rockies has surged: up 140% on the route-weighted index since 1970.

+140%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 →
169Routes 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 →
56YearsYears 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 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 →

Brewer's Sparrow has surged in Northern Rockies: up 140% on the route-weighted index since 1970.

Brewer's Sparrow In Northern Rockies Population Forecast

If the recent trend holds, Brewer's Sparrow in Northern Rockies is projected to fall about 29% by 2029 — from 19 in 2024 to a central estimate of 13 (95% range 6.5–20). A 5-year backtest shows a typical error of ±20.6%, with 100% of held-out values landing inside the 95% band.

-29%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 →
13Projected 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 →
6.5–2095% 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 →
±20.6%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 Northern Rockies is projected to fall about 29% by 2029 — from 19 in 2024 to a central estimate of 13 (95% range 6.5–20). A 5-year backtest shows a typical error of ±20.6%, with 100% of held-out values landing inside the 95% band.19682029
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 →
2025136.420
2026136.420
2027136.420
2028136.420
2029136.520

Routes In Northern Rockies

Routes recording Brewer's Sparrow in Northern Rockies.
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 →
Black Rock 2WYOMING1402024
Seedskadee 2WYOMING1262024
Bear CreekWYOMING1152024
RyegrassWYOMING1102024
Rawlins 2WYOMING1092024
Neponset ResUTAH1082018
Browns ParkCOLORADO982024
MeeteetseWYOMING942024
MckinnonWYOMING861986
Great DivideCOLORADO842024
BeaverheadMONTANA842024
BaggsWYOMING822024
Clover CreekOREGON802024
BairoilWYOMING802024
LayCOLORADO742024
Saleratus CrUTAH722018
MaybellCOLORADO692024
Patrick DrawWYOMING631980
RelianceWYOMING632018
LamontWYOMING622024
DiamondvilleWYOMING601982
Flamin GorgeWYOMING602024
Mtn ViewWYOMING592024
Elk Horn 2WYOMING582024
Sawtooth CtyIDAHO522014

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