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Species · California · BBS 2025 Release · 1966–2024

Nashville Warbler Population Trend in California

All statesForest birds

Nashville Warbler in California has surged: up 435% on the route-weighted index since 1970.

+435%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 →
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 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 435% 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 123% by 2029 — from 1.7 in 2024 to a central estimate of 3.9 (95% range 2.2–5.5). A 5-year backtest shows a typical error of ±67.8%, with 60% of held-out values landing inside the 95% band.

+123%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 →
3.9Projected 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 →
2.2–5.595% 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 →
±67.8%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 123% by 2029 — from 1.7 in 2024 to a central estimate of 3.9 (95% range 2.2–5.5). A 5-year backtest shows a typical error of ±67.8%, with 60% 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 →
20253.72.15.4
20263.82.15.4
20273.82.15.5
20283.82.25.5
20293.92.25.5

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
Johnsville3820241975
Carrville3619701970
Forest Hill 23420052005
Placerville3420241998
Bass Lake3220111972
Horse Creek3120191971
Downieville2520241975
Forest Hill2420221997
Riverton1920231973
Tahoe Nf1719941987
Hat Creek1620181973
Pilot Creek1619961994
Hay Fork1620172001
Lonesome Rdg1420141994
Tuolumne Grove1220241972
Butte Meadow1220141972
Wawona1220241998
Orleans1120121972
Tomhead1020111998
Eagle Lake920221984
Mccloud920211978
Whiskeytown920122002
Friday Ridge820241994
Lake Success719961980

Nashville Warbler Population Trend in Other States

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

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