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Species · California · BBS 2025 Release · 1966–2024

Hammond's Flycatcher Population Trend in California

All statesAerial insectivores

Hammond's Flycatcher in California has surged: up 493% on the route-weighted index since 1970.

+493%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 →
76Routes 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 Hammond's 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 →

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 →

Hammond's Flycatcher has surged in California: up 493% on the route-weighted index since 1970.

Hammond's Flycatcher Population Forecast in California

If the recent trend holds, Hammond's Flycatcher in California is projected to rise about 332% by 2029 — from 0.23 in 2024 to a central estimate of 0.98 (95% range 0.40–1.6). A 5-year backtest shows a typical error of ±159.8%, with 20% of held-out values landing inside the 95% band.

+332%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 →
0.98Projected 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 →
0.40–1.695% 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 →
±159.8%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, Hammond's Flycatcher in California is projected to rise about 332% by 2029 — from 0.23 in 2024 to a central estimate of 0.98 (95% range 0.40–1.6). A 5-year backtest shows a typical error of ±159.8%, 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 →
20250.950.371.5
20260.960.381.5
20270.960.381.5
20280.970.391.6
20290.980.401.6

Hammond's Flycatcher Survey Routes in California

Routes recording Hammond's 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 →
Lassen Park2119891972
Tionesta1820211997
Butte Meadow1820141972
Bartle1620211974
Hat Creek920181974
Riverton820231973
Eagle Lake720221972
Pilot Creek619961994
Forest Hill 2520052005
Junction Cty520111991
Macdoel520191978
Little Truckee520231997
Lumberyard520241977
Gazelle419951988
Tuolumne Grove420241973
Chester420161997
Meadow Valley420231999
Silver City420131995
Hullville320071968
French Gulch320102003
Tomhead320101999
Forest Hill320221997
Korbel320212013
Pine Mountain320162001
Westville220241971

Hammond's Flycatcher Population Trend in Other States

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