BirdAnalyst
Species · Arizona · BBS 2025 Release · 1966–2024

Brewer's Blackbird Population Trend in Arizona

All statesGeneralists

Brewer's Blackbird in Arizona has fallen sharply: down 61% on the route-weighted index since 1970.

-61%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 →
24Routes In StateSurvey 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 Brewer's Blackbird Trends in ArizonaNotable 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 fallen sharply in Arizona: down 61% on the route-weighted index since 1970.

Brewer's Blackbird Population Forecast in Arizona

If the recent trend holds, Brewer's Blackbird in Arizona is projected to fall about 19% by 2029 — from 0.63 in 2024 to a central estimate of 0.51 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±34.7%, with 100% of held-out values landing inside the 95% band.

-19%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 →
0.51Projected 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 →
0.00–1.695% 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 →
±34.7%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 Arizona is projected to fall about 19% by 2029 — from 0.63 in 2024 to a central estimate of 0.51 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±34.7%, 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 →
20250.580.001.7
20260.560.001.7
20270.550.001.6
20280.530.001.6
20290.510.001.6

Brewer's Blackbird Survey Routes in Arizona

Routes recording Brewer's Blackbird in Arizona.
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 →
Alpine3020231992
Maine1420241992
Blue919911975
Williams820191999
Happy Jack820241977
Round Rock619891968
Mormon Lake619751968
Casa Grande619911991
Black Mesa519951988
Laguna519841981
Florence419721968
Pinetop420211993
Peach Spring420121992
Sawmill320141989
San Simon319791976
Dry Park320141993
Hunt219961968
Sprucedale220221992
House Rock119941973
New River120101991
Skull Valley120212021
Palo Verde120071992
Tsaile120171993
Clay Spring120141990

Brewer's Blackbird Population Trend in Other States

californiacoloradoidahoindianamichiganminnesotamontananebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwisconsinwyoming

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