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

Costa's Hummingbird Population Trend in California

All statesGeneralists

Costa's Hummingbird in California has held roughly steady: up 6% on the route-weighted index since 1970.

+6%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 →
78Routes 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 Costa's Hummingbird 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 Costa's Hummingbird in California. See the full index history below.

Costa's Hummingbird Population Forecast in California

If the recent trend holds, Costa's Hummingbird in California is projected to fall about 48% by 2029 — from 0.53 in 2024 to a central estimate of 0.28 (95% range 0.00–0.67). A 5-year backtest shows a typical error of ±31.2%, with 100% of held-out values landing inside the 95% band.

-48%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 →
0.28Projected 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 →
0.00–0.6795% 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 →
±31.2%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, Costa's Hummingbird in California is projected to fall about 48% by 2029 — from 0.53 in 2024 to a central estimate of 0.28 (95% range 0.00–0.67). A 5-year backtest shows a typical error of ±31.2%, 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 →
20250.280.000.68
20260.280.000.68
20270.280.000.67
20280.280.000.67
20290.280.000.67

Costa's Hummingbird Survey Routes in California

Routes recording Costa's Hummingbird 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 →
Elsinore Mtn1920241970
Glamis1819951970
Foster Park1419931968
Angelus Oaks1320051993
Anza Borrego920241968
Oak Grove720241975
Jofegan 2420242024
Rumsey419781974
Willow Spgs419771971
Mt Pinos419831969
Moreno420241978
Jofegan420232006
Calif City320121979
Harbor Lake319741973
Eureka Val320241992
Ivanpah320191995
Iron Mtns320112009
Blythe319791974
Ventucopa319951981
Big Pine220231971
Onyx219981991
Valley Wells220191989
Sisquoc220121976
Adelaida219701970
Anza219951975

Costa's Hummingbird Population Trend in Other States

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