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

Bell's Vireo In Coastal California

All regionsCoastal CaliforniaForest birds

Bell's Vireo in Coastal California has surged: up 481% on the route-weighted index since 1976.

+481%Since 1976TrendPercent 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 →
13Routes 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 →
18YearsYears 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 →

Bell's Vireo has surged in Coastal California: up 481% on the route-weighted index since 1976.

Bell's Vireo In Coastal California Population Forecast

If the recent trend holds, Bell's Vireo in Coastal California is projected to fall about 71% by 2029 — from 0.34 in 2024 to a central estimate of 0.10 (95% range 0.00–0.24). A 5-year backtest shows a typical error of ±78.5%, with 40% of held-out values landing inside the 95% band.

-71%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 →
0.10Projected 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 →
0.00–0.2495% 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 →
±78.5%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, Bell's Vireo in Coastal California is projected to fall about 71% by 2029 — from 0.34 in 2024 to a central estimate of 0.10 (95% range 0.00–0.24). A 5-year backtest shows a typical error of ±78.5%, with 40% of held-out values landing inside the 95% band.19712029
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 →
20250.090.000.23
20260.090.000.23
20270.090.000.23
20280.100.000.24
20290.100.000.24

Routes In Coastal California

Routes recording Bell'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 →
Jofegan 2CALIFORNIA162024
San YsidroCALIFORNIA52019
Cp. PendletonCALIFORNIA22003
MorenoCALIFORNIA12012
Oak GroveCALIFORNIA12018
CoalingaCALIFORNIA11976
Orange CoveCALIFORNIA11997
PowayCALIFORNIA11979
Mesa GrandeCALIFORNIA12010
Cuyamaca PkCALIFORNIA11971
CrestonCALIFORNIA11976
AtwaterCALIFORNIA12012
JofeganCALIFORNIA12022

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