BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

Black-tailed Gnatcatcher Population Trend in California

All statesArid-land birds

Black-tailed Gnatcatcher in California has fallen sharply: down 74% on the route-weighted index since 1971.

-74%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 →
33Routes 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 →
54YearsYears 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-tailed Gnatcatcher 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 declinecomputed 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-tailed Gnatcatcher has fallen sharply in California: down 74% on the route-weighted index since 1971.

Black-tailed Gnatcatcher Population Forecast in California

If the recent trend holds, Black-tailed Gnatcatcher in California is projected to rise about 45% by 2029 — from 0.07 in 2024 to a central estimate of 0.09 (95% range 0.00–0.24). A 5-year backtest shows a typical error of ±87.1%, with 100% of held-out values landing inside the 95% band.

+45%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 →
0.09Projected 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 →
0.00–0.2495% 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 →
±87.1%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-tailed Gnatcatcher in California is projected to rise about 45% by 2029 — from 0.07 in 2024 to a central estimate of 0.09 (95% range 0.00–0.24). A 5-year backtest shows a typical error of ±87.1%, 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 →
20250.090.000.24
20260.090.000.24
20270.090.000.24
20280.090.000.24
20290.090.000.24

Black-tailed Gnatcatcher Survey Routes in California

Routes recording Black-tailed Gnatcatcher 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 →
Coachella Cn1920131973
Glamis1520181971
Blythe820031973
Havasu Lake720031978
Iron Mtns420182000
Valley Wells320191989
Anza Borrego320241968
Essex319891989
Flynn319951992
Mt Baldy219801970
Big Pine219961996
Ubehebe219811981
Parker Dam220071975
Ivanpah220192017
Tecopa220231979
Cottonwood220191973
Niland220241987
Imperial Dam220101976
Death Valley219811975
Elizabeth Lk119761976
Jacumba119761976
Cholla Gard.120181997
Brawley119991990
Goldstone119881988
Barstow119771977

Black-tailed Gnatcatcher Population Trend in Other States

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