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Species · California · BBS 2025 Release · 1966–2024

Black-throated Gray Warbler Population Trend in California

All statesForest birds

Black-throated Gray Warbler in California has surged: up 87% on the route-weighted index since 1970.

+87%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 →
133Routes 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 Black-throated Gray Warbler 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 →

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 California: up 87% on the route-weighted index since 1970.

Black-throated Gray Warbler Population Forecast in California

If the recent trend holds, Black-throated Gray Warbler in California is projected to rise about 70% by 2029 — from 1.9 in 2024 to a central estimate of 3.2 (95% range 1.8–4.7). A 5-year backtest shows a typical error of ±86.5%, with 20% of held-out values landing inside the 95% band.

+70%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 →
3.2Projected 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 →
1.8–4.795% 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 →
±86.5%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, Black-throated Gray Warbler in California is projected to rise about 70% by 2029 — from 1.9 in 2024 to a central estimate of 3.2 (95% range 1.8–4.7). A 5-year backtest shows a typical error of ±86.5%, with 20% 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 →
20253.21.74.6
20263.21.74.6
20273.21.74.6
20283.21.84.7
20293.21.84.7

Black-throated Gray Warbler Survey Routes in California

Routes recording Black-throated Gray Warbler 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 →
Horse Creek5420191970
Waterman Gap4820241972
Forest Hill3920221997
Forest Hill 23320052005
Hay Fork2520172001
Hough Springs2520071999
Orleans2420121972
Placerville2220241998
Martins Fy2120091976
Valyermo2020191971
Shasta Lake1520241972
Orleans 21520142014
Hiouchi1520142002
Alderpoint1420121974
Ship Mtn.1420171994
Honeydew1220171968
Big Flat1220142002
Silver City1120131978
Longvale1120231972
Butte Meadow1120141972
Bartlett Sps1120181973
Korbel1120241972
Cohasset1020241976
Whiskeytown1020122002
Strawberry1020191999

Black-throated Gray Warbler Population Trend in Other States

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