BirdAnalyst
Species · BCR 34 · BBS 2025 Release · 1966–2024

Brewer's Sparrow In Sierra Madre Occidental

All regionsSierra Madre OccidentalGeneralists

Brewer's Sparrow in Sierra Madre Occidental has collapsed: down 96% on the route-weighted index since 1989.

-96%Since 1989TrendPercent 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 →
5Routes 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 →
16YearsYears 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 Sierra Madre Occidental: down 96% on the route-weighted index since 1989.

Routes In Sierra Madre Occidental

Routes recording Brewer's Sparrow in Sierra Madre Occidental.
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 →
PomereneARIZONA101974
SunizonaARIZONA91988
Skull ValleyARIZONA12021
PinetopARIZONA12018
Clay SpringARIZONA12024

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