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

Hermit Warbler In Coastal California

All regionsCoastal CaliforniaForest birds

Hermit Warbler in Coastal California has surged: up 286% on the route-weighted index since 1973.

+286%Since 1973TrendPercent 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 →
23Routes 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 →
52YearsYears 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 →

Hermit Warbler has surged in Coastal California: up 286% on the route-weighted index since 1973.

Hermit Warbler In Coastal California Population Forecast

If the recent trend holds, Hermit Warbler in Coastal California is projected to rise about 315% by 2029 — from 0.09 in 2024 to a central estimate of 0.35 (95% range 0.06–0.65). A 5-year backtest shows a typical error of ±298.9%, with 0% of held-out values landing inside the 95% band.

+315%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 →
0.35Projected 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 →
0.06–0.6595% 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 →
±298.9%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, Hermit Warbler in Coastal California is projected to rise about 315% by 2029 — from 0.09 in 2024 to a central estimate of 0.35 (95% range 0.06–0.65). A 5-year backtest shows a typical error of ±298.9%, with 0% of held-out values landing inside the 95% band.19712029
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 →
20250.330.040.63
20260.340.040.63
20270.340.050.64
20280.350.050.64
20290.350.060.65

Routes In Coastal California

Routes recording Hermit 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 →
Bartlett SpsCALIFORNIA52018
Waterman GapCALIFORNIA42024
TomheadCALIFORNIA32011
Hough SpringsCALIFORNIA32006
StonyfordCALIFORNIA32018
Point ReyesCALIFORNIA22022
CohassetCALIFORNIA21984
FairfaxCALIFORNIA22019
Glen EllenCALIFORNIA22003
Glen Ellen 2CALIFORNIA22018
CalpellaCALIFORNIA11986
Mt PinosCALIFORNIA11993
CoalingaCALIFORNIA11997
ValyermoCALIFORNIA12018
Lockwood ValCALIFORNIA11977
Elsinore MtnCALIFORNIA11973
Green ValleyCALIFORNIA12014
Lake CachumaCALIFORNIA12003
White RiverCALIFORNIA11973
TehamaCALIFORNIA12021
Angelus OaksCALIFORNIA12004
PescaderoCALIFORNIA12023
Cal Hot SpgsCALIFORNIA12015

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