BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

American Bittern In Coastal California

All regionsCoastal CaliforniaWetland birds

American Bittern in Coastal California has declined: down 34% on the route-weighted index since 1972.

-34%Since 1972TrendPercent 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 →
22Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
51YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 American Bittern in Coastal California. See the full index history below.

American Bittern In Coastal California Population Forecast

If the recent trend holds, American Bittern in Coastal California is projected to stay roughly flat through 2029, near 0.33 (95% range 0.00–0.99). A 5-year backtest shows a typical error of ±1210.5%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.33Projected 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 →
0.00–0.9995% 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 →
±1210.5%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, American Bittern in Coastal California is projected to stay roughly flat through 2029, near 0.33 (95% range 0.00–0.99). A 5-year backtest shows a typical error of ±1210.5%, 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 →
20250.350.001.0
20260.340.001.00
20270.340.000.99
20280.340.000.99
20290.330.000.99

Routes In Coastal California

Routes recording American Bittern in Coastal 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 →
GlennCALIFORNIA132023
CordovaCALIFORNIA31975
PenningtonCALIFORNIA22014
ArvinCALIFORNIA21985
TranquillityCALIFORNIA22003
Ora LomaCALIFORNIA21983
AthloneCALIFORNIA21982
Red BluffCALIFORNIA12014
CollegevilleCALIFORNIA11979
HughsonCALIFORNIA11987
OilfieldsCALIFORNIA11968
GravesboroCALIFORNIA11985
OrlandCALIFORNIA12015
CrestonCALIFORNIA12002
ShafterCALIFORNIA11986
AtwaterCALIFORNIA12007
Gold HillCALIFORNIA11986
OrovilleCALIFORNIA12008
TehamaCALIFORNIA11988
Yolla BollyCALIFORNIA11997
ZamoraCALIFORNIA11988
Staten Is.CALIFORNIA12024

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