BirdAnalyst
Species · BCR 9 · BBS 2026 Release · 1966–2025

Cassin's Vireo In Great Basin

All regionsGreat BasinForest birds

Cassin's Vireo in Great Basin has surged: up 86% on the route-weighted index since 1970.

+86%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 →
78Routes 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 →
57YearsYears 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 Great Basin: up 86% on the route-weighted index since 1970.

Cassin's Vireo In Great Basin Population Forecast

If the recent trend holds, Cassin's Vireo in Great Basin is projected to rise about 58% by 2030 — from 0.74 in 2025 to a central estimate of 1.2 (95% range 0.81–1.5). A 5-year backtest shows a typical error of ±25.2%, with 80% of held-out values landing inside the 95% band.

+58%Change by 2030TrendPercent 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 →
1.2Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.81–1.595% 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 →
±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 Great Basin is projected to rise about 58% by 2030 — from 0.74 in 2025 to a central estimate of 1.2 (95% range 0.81–1.5). A 5-year backtest shows a typical error of ±25.2%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20261.10.751.5
20271.10.771.5
20281.10.781.5
20291.20.801.5
20301.20.811.5

Routes In Great Basin

Routes recording Cassin's Vireo in Great Basin.
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 →
EwanWASHINGTON321995
Badger CreekOREGON172025
BartleCALIFORNIA142021
ChinchaloOREGON112025
Davis LakeOREGON102025
Medicine Mtn.CALIFORNIA82021
E. Mt. AdamsWASHINGTON82025
CarltonWASHINGTON72022
PauninaOREGON62025
LakeviewOREGON62025
HackamoreCALIFORNIA52010
RimrockWASHINGTON52025
SnowdenWASHINGTON52024
MacdoelCALIFORNIA42019
Camp ShermanOREGON41996
Wizard FallsOREGON42025
NewhalemWASHINGTON42025
LeavenworthWASHINGTON42024
Blewett PassWASHINGTON42025
PaisleyOREGON32025
TwispWASHINGTON32024
ArdenvoirWASHINGTON31987
RonaldWASHINGTON32025
MazamaWASHINGTON32022
MadelineCALIFORNIA22023

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.