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Species · California · BBS 2026 Release · 1966–2025

Orange-crowned Warbler Population Trend in California

All statesForest birds

Orange-crowned Warbler in California has edged up: up 24% on the route-weighted index since 1970.

+24%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 →
176Routes 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 Orange-crowned 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 →

No notable trend signals for Orange-crowned Warbler in California. See the full index history below.

Orange-crowned Warbler Population Forecast in California

If the recent trend holds, Orange-crowned Warbler in California is projected to rise about 56% by 2030 — from 2.4 in 2025 to a central estimate of 3.7 (95% range 1.9–5.4). A 5-year backtest shows a typical error of ±53.7%, with 80% of held-out values landing inside the 95% band.

+56%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 →
1.9–5.495% 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 →
±53.7%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, Orange-crowned Warbler in California is projected to rise about 56% by 2030 — from 2.4 in 2025 to a central estimate of 3.7 (95% range 1.9–5.4). A 5-year backtest shows a typical error of ±53.7%, 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 →
20263.71.95.4
20273.71.95.4
20283.71.95.4
20293.71.95.4
20303.71.95.4

Orange-crowned Warbler Survey Routes in California

Routes recording Orange-crowned 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 →
Rumsey4520081980
Santa Cruz I4219881988
Harbor Lake 24120242014
Shasta Lake3320251972
Longvale3320231972
Glen Ellen3020041972
Honeydew2920171968
S Catalina2320251988
Chilcoot2220092009
Carmel Val2020251973
Bartlett Sps1920181973
Hay Fork1720172001
Alderpoint1520121974
Redwood N.P.1320101995
Cohasset1220251973
Poway1219801974
Folsom1220251984
Higgins Corn1220251973
Fairfax1120191972
Adelaida1120151970
Orleans1120121973
Laytonville1120251972
Jofegan 21020252024
Martins Fy1020091976
Elsinore Mtn1020241970

Orange-crowned Warbler Population Trend in Other States

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