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Species · California · BBS 2025 Release · 1966–2024

Orange-crowned Warbler Population Trend in California

All statesForest birds

Orange-crowned Warbler in California has increased: up 32% on the route-weighted index since 1970.

+32%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 →
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 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 31% by 2029 — from 2.9 in 2024 to a central estimate of 3.8 (95% range 2.0–5.5). A 5-year backtest shows a typical error of ±39.7%, with 100% of held-out values landing inside the 95% band.

+31%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 →
3.8Projected 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 →
2.0–5.595% 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 →
±39.7%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 31% by 2029 — from 2.9 in 2024 to a central estimate of 3.8 (95% range 2.0–5.5). A 5-year backtest shows a typical error of ±39.7%, with 100% 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 →
20253.82.05.5
20263.82.05.5
20273.82.05.5
20283.82.05.5
20293.82.05.5

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
S Catalina4420221988
Santa Cruz I4219881988
Harbor Lake 24120242014
Carmel Val3620241973
Longvale3320231972
Glen Ellen3020041972
Honeydew2920171968
Chilcoot2220092009
Folsom2120241984
Bartlett Sps1920181973
Coyote1920221972
Waterman Gap1720241975
Hay Fork1720172001
Alderpoint1520121974
Cohasset1420241973
Redwood N.P.1320101995
Jofegan 21220242024
Point Reyes1220231970
Poway1219801974
Laytonville1220241972
Higgins Corn1220241973
Holmes1120241968
Fairfax1120191972
Adelaida1120151970

Orange-crowned Warbler Population Trend in Other States

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