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

Black-throated Gray Warbler In Coastal California

All regionsCoastal CaliforniaForest birds

Black-throated Gray Warbler in Coastal California has surged: up 881% on the route-weighted index since 1970.

+881%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 →
49Routes 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 →
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 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-throated Gray Warbler has surged in Coastal California: up 881% on the route-weighted index since 1970.

Forecast

If the recent trend holds, Black-throated Gray Warbler in Coastal California is projected to stay roughly flat through 2029, near 1.5 (95% range 0.85–2.2). A 5-year backtest shows a typical error of ±28.7%, with 100% of held-out values landing inside the 95% band.

-7%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 →
1.5Projected 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 →
0.85–2.295% 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 →
±28.7%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, Black-throated Gray Warbler in Coastal California is projected to stay roughly flat through 2029, near 1.5 (95% range 0.85–2.2). A 5-year backtest shows a typical error of ±28.7%, 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 →
20251.40.782.1
20261.50.802.1
20271.50.822.1
20281.50.832.1
20291.50.852.2

Routes In Coastal California

Routes recording Black-throated Gray Warbler 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 →
Waterman GapCALIFORNIA482024
Hough SpringsCALIFORNIA252007
ValyermoCALIFORNIA202019
Bartlett SpsCALIFORNIA112018
CohassetCALIFORNIA102024
Carmel ValCALIFORNIA82024
StonyfordCALIFORNIA82018
WoodlandsCALIFORNIA62024
Lake Hemet 2CALIFORNIA52023
TehamaCALIFORNIA42022
Glen EllenCALIFORNIA42003
Point ReyesCALIFORNIA32010
FallsvaleCALIFORNIA31974
LockwoodCALIFORNIA32023
Angelus OaksCALIFORNIA32016
Yokohl ValCALIFORNIA21996
FolsomCALIFORNIA22009
Mt LagunaCALIFORNIA21980
CoyoteCALIFORNIA22022
CopperopolisCALIFORNIA21999
PescaderoCALIFORNIA22024
TomheadCALIFORNIA22008
AlamarCALIFORNIA22015
Red BluffCALIFORNIA11997
CalpellaCALIFORNIA11986

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