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

Black-crowned Night Heron In Coastal California

All regionsCoastal CaliforniaWetland birds

Black-crowned Night Heron in Coastal California has surged: up 119% on the route-weighted index since 1971.

+119%Since 1971TrendPercent 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 →
52Routes 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 →
55YearsYears 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 →

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 →

Black-crowned Night Heron has surged in Coastal California: up 119% on the route-weighted index since 1971.

Black-crowned Night Heron In Coastal California Population Forecast

If the recent trend holds, Black-crowned Night Heron in Coastal California is projected to rise about 48% by 2029 — from 0.30 in 2024 to a central estimate of 0.44 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±885.9%, 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 →
0.44Projected 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 →
0.00–1.695% 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 →
±885.9%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, Black-crowned Night Heron in Coastal California is projected to rise about 48% by 2029 — from 0.30 in 2024 to a central estimate of 0.44 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±885.9%, 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 →
20250.470.001.7
20260.460.001.7
20270.460.001.6
20280.450.001.6
20290.440.001.6

Routes In Coastal California

Routes recording Black-crowned Night Heron 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 →
Ora LomaCALIFORNIA281983
OrlandCALIFORNIA92014
Buena VistaCALIFORNIA62019
BakersfieldCALIFORNIA52023
MorenoCALIFORNIA52024
Harbor LakeCALIFORNIA41991
Foster ParkCALIFORNIA31993
AtwaterCALIFORNIA32007
Red BluffCALIFORNIA21992
CollegevilleCALIFORNIA21975
Orange CoveCALIFORNIA22004
CohassetCALIFORNIA21985
PowayCALIFORNIA21980
SisquocCALIFORNIA21994
Cp. PendletonCALIFORNIA21993
ArvinCALIFORNIA22016
OrovilleCALIFORNIA22024
MoragaCALIFORNIA22004
Mark WestCALIFORNIA22024
CoyoteCALIFORNIA22024
OnealsCALIFORNIA21983
Glen EllenCALIFORNIA21996
PenningtonCALIFORNIA11995
RumseyCALIFORNIA11990
ColmaCALIFORNIA11968

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