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Species · California · BBS 2026 Release · 1966–2025

Nashville Warbler Population Trend in California

All statesForest birds

Nashville Warbler in California has surged: up 319% on the route-weighted index since 1970.

+319%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 →
107Routes 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 →
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 Nashville Warbler 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 →

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 →

Nashville Warbler has surged in California: up 319% on the route-weighted index since 1970.

Nashville Warbler Population Forecast in California

If the recent trend holds, Nashville Warbler in California is projected to rise about 161% by 2030 — from 1.4 in 2025 to a central estimate of 3.7 (95% range 2.0–5.5). A 5-year backtest shows a typical error of ±95.8%, with 40% of held-out values landing inside the 95% band.

+161%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 →
3.7Projected 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 →
2.0–5.595% 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 →
±95.8%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, Nashville Warbler in California is projected to rise about 161% by 2030 — from 1.4 in 2025 to a central estimate of 3.7 (95% range 2.0–5.5). A 5-year backtest shows a typical error of ±95.8%, with 40% 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 →
20263.61.95.3
20273.61.95.4
20283.71.95.4
20293.71.95.4
20303.72.05.5

Nashville Warbler Survey Routes in California

Routes recording Nashville Warbler 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 →
South Fork Mtn4220222000
Carrville3619701970
Forest Hill 23420052005
Bass Lake3220111972
Horse Creek3120191971
Placerville2320251998
Tahoe Nf1719941987
Hat Creek1620181973
Pilot Creek1619961994
Hay Fork1620172001
Tuolumne Grove1520251972
Riverton1420251973
Lonesome Rdg1420141994
Johnsville1220251975
Butte Meadow1220141972
Orleans1120121972
Downieville1020251975
Tomhead1020111998
Mccloud920211978
Whiskeytown920122002
Wawona920251998
Lake Success719961980
Lumberyard720251978
Greenhorn Mt720081971
White River719921973

Nashville Warbler Population Trend in Other States

connecticutidahomainemarylandmassachusettsmichiganminnesotamontananew-hampshirenew-jerseynew-yorknorth-dakotaoregonpennsylvaniarhode-islandvermontvirginiawashingtonwest-virginiawisconsin

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