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

Willow Flycatcher Population Trend in California

All statesAerial insectivores

Willow Flycatcher in California has fallen sharply: down 52% on the route-weighted index since 1971.

-52%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 →
72Routes 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 →
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 Willow Flycatcher 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 →

No notable trend signals for Willow Flycatcher in California. See the full index history below.

Willow Flycatcher Population Forecast in California

If the recent trend holds, Willow Flycatcher in California is projected to stay roughly flat through 2029, near 0.11 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±544.2%, with 60% of held-out values landing inside the 95% band.

n/aChange 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 →
0.11Projected 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 →
0.00–0.2395% 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 →
±544.2%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, Willow Flycatcher in California is projected to stay roughly flat through 2029, near 0.11 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±544.2%, with 60% of held-out values landing inside the 95% band.19692029
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 →
20250.110.000.23
20260.110.000.23
20270.110.000.23
20280.110.000.23
20290.110.000.23

Willow Flycatcher Survey Routes in California

Routes recording Willow Flycatcher 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 Creek1220191974
Mt Shasta719761976
Coalinga719951995
Dorris620191993
Genesee619741974
Yreka620071985
Last Chance319981998
Korbel320232003
Ukiah319891989
Mt Baldy220162016
Eagle Lake219751975
Iron Gate220191989
Riovista219761976
Glenn220052005
Davis Creek219791979
Moreno220192012
Riverton219741973
Athlone220042004
Lakeshore219811980
Kelso Valley120181973
Green Valley119981971
Crescent Cty120182001
Honeydew120092009
Holmes120061983
Red Bluff119891989

Willow Flycatcher Population Trend in Other States

alaskaarizonaarkansascoloradoconnecticutdelawaregeorgiaidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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