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

Brewer's Blackbird In Sierra Madre Occidental

All regionsSierra Madre OccidentalGeneralists

Brewer's Blackbird in Sierra Madre Occidental has collapsed: down 76% on the route-weighted index since 1970.

-76%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 →
54YearsYears 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 76% 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 83% by 2029 — from 1.2 in 2024 to a central estimate of 0.20 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±68.9%, with 100% of held-out values landing inside the 95% band.

-83%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 →
0.20Projected 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 →
0.00–2.295% 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 →
±68.9%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 83% by 2029 — from 1.2 in 2024 to a central estimate of 0.20 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±68.9%, 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 →
20250.410.002.5
20260.360.002.4
20270.310.002.4
20280.260.002.3
20290.200.002.2

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 →
AlpineARIZONA302023
MaineARIZONA142024
BlueARIZONA91991
WilliamsARIZONA82019
Happy JackARIZONA82024
Mormon LakeARIZONA61975
PinetopARIZONA42021
San SimonARIZONA31979
SprucedaleARIZONA22022
Skull ValleyARIZONA12021
Clay SpringARIZONA12014

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