BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

Cassin's Vireo In Sierra Nevada

All regionsSierra NevadaForest birds

Cassin's Vireo in Sierra Nevada has edged up: up 21% on the route-weighted index since 1972.

+21%Since 1972TrendPercent 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 →
37Routes 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 →

No notable trend signals for Cassin's Vireo in Sierra Nevada. See the full index history below.

Cassin's Vireo In Sierra Nevada Population Forecast

If the recent trend holds, Cassin's Vireo in Sierra Nevada is projected to rise about 48% by 2029 — from 5.5 in 2024 to a central estimate of 8.2 (95% range 5.5–11). A 5-year backtest shows a typical error of ±25.2%, with 80% of held-out values landing inside the 95% band.

+48%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 →
8.2Projected 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 →
5.5–1195% 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 →
±25.2%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 Sierra Nevada is projected to rise about 48% by 2029 — from 5.5 in 2024 to a central estimate of 8.2 (95% range 5.5–11). A 5-year backtest shows a typical error of ±25.2%, with 80% 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 →
20257.95.111
20267.95.211
20278.05.311
20288.15.411
20298.25.511

Routes In Sierra Nevada

Routes recording Cassin's Vireo in Sierra Nevada.
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 →
Forest HillCALIFORNIA272022
Butte MeadowCALIFORNIA262014
LumberyardCALIFORNIA182024
Forest Hill 2CALIFORNIA182005
RivertonCALIFORNIA172023
DownievilleCALIFORNIA142024
GeneseeCALIFORNIA132024
PlacervilleCALIFORNIA122024
ChesterCALIFORNIA112017
Eagle LakeCALIFORNIA92024
WestvilleCALIFORNIA92024
StrawberryCALIFORNIA92019
JohnsvilleCALIFORNIA52024
Tuolumne GroveCALIFORNIA52024
Hat CreekCALIFORNIA52018
Last ChanceCALIFORNIA52019
Chaos CraterCALIFORNIA42019
PaxtonCALIFORNIA42024
WawonaCALIFORNIA42024
ChilcootCALIFORNIA42024
Cottage SpgsCALIFORNIA31975
Bass LakeCALIFORNIA32018
GoumazCALIFORNIA32011
DardanelleCALIFORNIA22018
WoodfordsCALIFORNIA22024

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