BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

Willow Flycatcher In Sierra Nevada

All regionsSierra NevadaAerial insectivores

Willow Flycatcher in Sierra Nevada has collapsed: down 86% on the route-weighted index since 1974.

-86%Since 1974TrendPercent 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 →
13Routes 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 →
31YearsYears 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 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 →

Willow Flycatcher has collapsed in Sierra Nevada: down 86% on the route-weighted index since 1974.

Forecast

If the recent trend holds, Willow Flycatcher in Sierra Nevada is projected to fall about 100% by 2029 — from 0.05 in 2024 to a central estimate of 0.00 (95% range 0.00–0.25). A 5-year backtest shows a typical error of ±182.5%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–0.2595% 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 →
±182.5%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, Willow Flycatcher in Sierra Nevada is projected to fall about 100% by 2029 — from 0.05 in 2024 to a central estimate of 0.00 (95% range 0.00–0.25). A 5-year backtest shows a typical error of ±182.5%, with 100% of held-out values landing inside the 95% band.19722029
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 →
20250.000.000.25
20260.000.000.25
20270.000.000.25
20280.000.000.25
20290.000.000.25

Routes In Sierra Nevada

Routes recording Willow Flycatcher in Sierra Nevada.
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 →
GeneseeCALIFORNIA61974
Last ChanceCALIFORNIA31998
Eagle LakeCALIFORNIA21975
RivertonCALIFORNIA21974
LakeshoreCALIFORNIA21981
Bass LakeCALIFORNIA12011
WoodfordsCALIFORNIA12022
Kings CanyonCALIFORNIA11984
Tuolumne GroveCALIFORNIA12024
Butte MeadowCALIFORNIA11974
Chaos CraterCALIFORNIA11996
PaxtonCALIFORNIA12017
Little TruckeeCALIFORNIA12019

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