BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Swainson's Hawk In Coastal California

All regionsCoastal CaliforniaGeneralists

Swainson's Hawk in Coastal California has surged: up 27× on the route-weighted index since 1975.

27×Since 1975TrendPercent 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 →
25Routes 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 →
49YearsYears 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 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 →

Swainson's Hawk has surged in Coastal California: up 27× on the route-weighted index since 1975.

Swainson's Hawk In Coastal California Population Forecast

If the recent trend holds, Swainson's Hawk in Coastal California is projected to rise about 11% by 2029 — from 1.6 in 2024 to a central estimate of 1.8 (95% range 0.11–3.4). A 5-year backtest shows a typical error of ±78.3%, with 100% of held-out values landing inside the 95% band.

+11%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 →
1.8Projected 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 →
0.11–3.495% 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 →
±78.3%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, Swainson's Hawk in Coastal California is projected to rise about 11% by 2029 — from 1.6 in 2024 to a central estimate of 1.8 (95% range 0.11–3.4). A 5-year backtest shows a typical error of ±78.3%, 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 →
20251.60.003.3
20261.70.003.3
20271.70.033.4
20281.70.073.4
20291.80.113.4

Routes In Coastal California

Routes recording Swainson's Hawk in Coastal 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 →
Collegeville 2CALIFORNIA422023
Ora LomaCALIFORNIA292024
AthloneCALIFORNIA242007
AtwaterCALIFORNIA142012
WestleyCALIFORNIA132024
ZamoraCALIFORNIA102024
Staten Is.CALIFORNIA92024
Buena VistaCALIFORNIA82019
Tracy 2CALIFORNIA62024
CollegevilleCALIFORNIA22004
HughsonCALIFORNIA22024
TranquillityCALIFORNIA22024
TracyCALIFORNIA22009
PenningtonCALIFORNIA12023
RiovistaCALIFORNIA12022
CohassetCALIFORNIA12024
OrlandCALIFORNIA12017
SangerCALIFORNIA12015
Carrizo PlnCALIFORNIA12022
GlennCALIFORNIA12009
CordovaCALIFORNIA11975
OrovilleCALIFORNIA12024
CoyoteCALIFORNIA12019
OnealsCALIFORNIA12024
PolomaCALIFORNIA12024

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