BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Cassin's Vireo In Coastal California

All regionsCoastal CaliforniaForest birds

Cassin's Vireo in Coastal California has surged: up 155% on the route-weighted index since 1970.

+155%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 →
60Routes 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 →
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 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 increasecomputed 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 →

Cassin's Vireo has surged in Coastal California: up 155% on the route-weighted index since 1970.

Cassin's Vireo In Coastal California Population Forecast

If the recent trend holds, Cassin's Vireo in Coastal California is projected to rise about 170% by 2029 — from 0.34 in 2024 to a central estimate of 0.92 (95% range 0.37–1.5). A 5-year backtest shows a typical error of ±125.7%, with 40% of held-out values landing inside the 95% band.

+170%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 →
0.92Projected 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 →
0.37–1.595% 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 →
±125.7%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, Cassin's Vireo in Coastal California is projected to rise about 170% by 2029 — from 0.34 in 2024 to a central estimate of 0.92 (95% range 0.37–1.5). A 5-year backtest shows a typical error of ±125.7%, with 40% 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 →
20250.890.341.4
20260.900.351.4
20270.910.361.5
20280.910.361.5
20290.920.371.5

Routes In Coastal California

Routes recording Cassin's Vireo in Coastal California.
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 →
StonyfordCALIFORNIA202018
Bartlett SpsCALIFORNIA132018
Hough SpringsCALIFORNIA132007
CalpellaCALIFORNIA81986
CohassetCALIFORNIA72024
Glen EllenCALIFORNIA62004
Glen Ellen 2CALIFORNIA62023
SisquocCALIFORNIA42000
TehamaCALIFORNIA42022
MoragaCALIFORNIA42011
Waterman GapCALIFORNIA42024
White RiverCALIFORNIA31991
Gold HillCALIFORNIA32017
Mark WestCALIFORNIA32019
TomheadCALIFORNIA32011
Santa YnezCALIFORNIA22014
JacksonCALIFORNIA21992
Lake Hemet 2CALIFORNIA22023
Angelus OaksCALIFORNIA22017
PolomaCALIFORNIA22016
AlamarCALIFORNIA22003
Red BluffCALIFORNIA12022
RumseyCALIFORNIA12007
Yokohl ValCALIFORNIA11993
Foster ParkCALIFORNIA11986

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