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Species · California · BBS 2025 Release · 1966–2024

Cassin's Vireo Population Trend in California

All statesForest birds

Cassin's Vireo in California has surged: up 287% on the route-weighted index since 1970.

+287%Since 1970
156Routes In State
56Years

Notable Cassin's Vireo Trends in California

long arc increasecomputed index

Cassin's Vireo has surged in California: up 287% on the route-weighted index since 1970.

Cassin's Vireo Population Forecast in California

If the recent trend holds, Cassin's Vireo in California is projected to rise about 117% by 2029 — from 1.7 in 2024 to a central estimate of 3.8 (95% range 2.4–5.2). A 5-year backtest shows a typical error of ±111.4%, with 0% of held-out values landing inside the 95% band.

+117%Change by 2029
3.8Projected 2029 index
2.4–5.295% range
±111.4%Backtest error
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 index95% low95% high
20253.62.25.0
20263.72.35.1
20273.72.35.1
20283.72.35.1
20293.82.45.2

Cassin's Vireo Survey Routes in California

Routes recording Cassin's Vireo in California.
Horse Creek4420191970
Forest Hill2720221997
Butte Meadow2620141972
Orleans 22320142014
Alderpoint2120121974
Stonyford2020182015
Forest Hill 21820052005
Lumberyard1820241997
Martins Fy1720091976
Riverton1720231997
Longvale1420231972
Downieville1420241975
Bartle1420211972
Genesee1320241972
Bartlett Sps1320181974
Hough Springs1320071999
Shasta Lake1220241972
Placerville1220241997
Friday Ridge1220241994
Hullville1120191968
Chester1120171997
Orleans1020121972
Hay Fork1020172004
Eagle Lake920241972
Westville920241971

Cassin's Vireo Population Trend in Other States

alaskaidahomontanaoregonwashington

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