BirdAnalyst
Species · BCR 32 · BBS 2026 Release · 1966–2025

Swainson's Hawk In Coastal California

All regionsCoastal CaliforniaBirds of prey

Swainson's Hawk in Coastal California has surged: up 34× on the route-weighted index since 1975.

34×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 →
50YearsYears 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 34× 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 stay roughly flat through 2030, near 1.8 (95% range 0.16–3.4). A 5-year backtest shows a typical error of ±54.5%, with 100% of held-out values landing inside the 95% band.

+9%Change by 2030TrendPercent 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 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.16–3.495% 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 →
±54.5%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, Swainson's Hawk in Coastal California is projected to stay roughly flat through 2030, near 1.8 (95% range 0.16–3.4). A 5-year backtest shows a typical error of ±54.5%, with 100% of held-out values landing inside the 95% band.19722030
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 →
20261.70.023.3
20271.70.053.3
20281.70.093.4
20291.80.133.4
20301.80.163.4

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 LomaCALIFORNIA312025
AthloneCALIFORNIA242007
WestleyCALIFORNIA152025
AtwaterCALIFORNIA142012
Buena VistaCALIFORNIA82019
ZamoraCALIFORNIA72025
Tracy 2CALIFORNIA62024
HughsonCALIFORNIA52025
Staten Is.CALIFORNIA42025
CollegevilleCALIFORNIA22004
TranquillityCALIFORNIA22024
TracyCALIFORNIA22009
PenningtonCALIFORNIA12025
RiovistaCALIFORNIA12022
CohassetCALIFORNIA12024
OrlandCALIFORNIA12017
SangerCALIFORNIA12015
Carrizo PlnCALIFORNIA12022
GlennCALIFORNIA12009
CordovaCALIFORNIA11975
OrovilleCALIFORNIA12024
CoyoteCALIFORNIA12019
OnealsCALIFORNIA12024
PolomaCALIFORNIA12024

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.