BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

Warbling Vireo Population Trend in California

All statesForest birds

Warbling Vireo in California has increased: up 34% on the route-weighted index since 1970.

+34%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 →
182Routes In StateSurvey 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 Warbling Vireo Trends in CaliforniaNotable 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 Warbling Vireo in California. See the full index history below.

Warbling Vireo Population Forecast in California

If the recent trend holds, Warbling Vireo in California is projected to rise about 36% by 2029 — from 3.8 in 2024 to a central estimate of 5.1 (95% range 3.5–6.7). A 5-year backtest shows a typical error of ±38.5%, with 40% of held-out values landing inside the 95% band.

+36%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 →
5.1Projected 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 →
3.5–6.795% 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 →
±38.5%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, Warbling Vireo in California is projected to rise about 36% by 2029 — from 3.8 in 2024 to a central estimate of 5.1 (95% range 3.5–6.7). A 5-year backtest shows a typical error of ±38.5%, 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 →
20255.03.46.6
20265.13.46.7
20275.13.56.7
20285.13.56.7
20295.13.56.7

Warbling Vireo Survey Routes in California

Routes recording Warbling Vireo in 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 →
Waterman Gap5020241972
Point Reyes4720231970
Honeydew3420171968
Little Truckee2520231997
Genesee2420241972
Pescadero2420241992
Carmel Val2120241973
Holmes2020241968
Woodfords2020241973
Riverton1720231973
Fairfax1620241972
Alderpoint1620121974
Meadow Valley1520241999
Tuolumne Grove1420241972
Johnsville1320241975
Bartle1320211972
Horse Creek1220191971
Macdoel1220191974
Korbel1220241972
Cottage Spgs1119681968
Dardanelle1120191972
Lumberyard1120241976
Westville1020241971
Butte Meadow1020141972
Hay Fork1020132005

Warbling Vireo Population Trend in Other States

alabamaalaskaarizonaarkansascoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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