BirdAnalyst
Species · BCR 33 · BBS 2025 Release · 1966–2024

Brewer's Sparrow In Sonoran and Mojave Deserts

All regionsSonoran and Mojave DesertsGeneralists

Brewer's Sparrow in Sonoran and Mojave Deserts has collapsed: down 80% on the route-weighted index since 1972.

-80%Since 1972TrendPercent 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 →
25Routes 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 →
50YearsYears 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 collapsed in Sonoran and Mojave Deserts: down 80% on the route-weighted index since 1972.

Brewer's Sparrow In Sonoran and Mojave Deserts Population Forecast

If the recent trend holds, Brewer's Sparrow in Sonoran and Mojave Deserts is projected to fall about 100% by 2029 — from 0.17 in 2024 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–1.395% 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 →
±85%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 Sonoran and Mojave Deserts is projected to fall about 100% by 2029 — from 0.17 in 2024 to a central estimate of 0.00 (95% range 0.00–1.3). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20250.010.001.3
20260.000.001.3
20270.000.001.3
20280.000.001.3
20290.000.001.3

Routes In Sonoran and Mojave Deserts

Routes recording Brewer's Sparrow in Sonoran and Mojave Deserts.
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 →
Willow SpgsCALIFORNIA111977
Eureka ValCALIFORNIA72016
Silver PeakNEVADA71973
TecopaCALIFORNIA61987
Joshua TreeCALIFORNIA61991
OnyxCALIFORNIA51998
Calif CityCALIFORNIA41978
Alamo Res.ARIZONA31992
WildroseCALIFORNIA32021
Greenwater VCALIFORNIA32024
Haiwee ResCALIFORNIA22001
Valley WellsCALIFORNIA22003
Val Of FireNEVADA22017
AntaresARIZONA12024
UbehebeCALIFORNIA12021
DarwinCALIFORNIA12005
IvanpahCALIFORNIA12003
CimaCALIFORNIA11993
Lone PineCALIFORNIA12009
Death ValleyCALIFORNIA12023
Kelso ValleyCALIFORNIA12024
Cholla Gard.CALIFORNIA12015
Jean LakeNEVADA12010
Silver Peak 2NEVADA12018
Ash MeadowsNEVADA11998

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