BirdAnalyst
Species · BCR 34 · BBS 2026 Release · 1966–2025

Brewer's Blackbird In Sierra Madre Occidental

All regionsSierra Madre OccidentalGeneralists

Brewer's Blackbird in Sierra Madre Occidental has collapsed: down 75% on the route-weighted index since 1970.

-75%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 →
11Routes 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 →
55YearsYears 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 Blackbird has collapsed in Sierra Madre Occidental: down 75% on the route-weighted index since 1970.

Brewer's Blackbird In Sierra Madre Occidental Population Forecast

If the recent trend holds, Brewer's Blackbird in Sierra Madre Occidental is projected to fall about 82% by 2030 — from 1.3 in 2025 to a central estimate of 0.22 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±79.8%, with 100% of held-out values landing inside the 95% band.

-82%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 →
0.22Projected 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 →
0.00–2.395% 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 →
±79.8%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 Blackbird in Sierra Madre Occidental is projected to fall about 82% by 2030 — from 1.3 in 2025 to a central estimate of 0.22 (95% range 0.00–2.3). A 5-year backtest shows a typical error of ±79.8%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20260.420.002.5
20270.370.002.4
20280.320.002.4
20290.270.002.3
20300.220.002.3

Routes In Sierra Madre Occidental

Routes recording Brewer's Blackbird 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 →
AlpineARIZONA202025
BlueARIZONA91991
Mormon LakeARIZONA61975
MaineARIZONA62025
PinetopARIZONA42021
Happy JackARIZONA42025
San SimonARIZONA31979
SprucedaleARIZONA32025
WilliamsARIZONA12025
Skull ValleyARIZONA12021
Clay SpringARIZONA12014

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