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

Violet-green Swallow In Coastal California

All regionsCoastal CaliforniaAerial insectivores

Violet-green Swallow in Coastal California has fallen sharply: down 58% on the route-weighted index since 1970.

-58%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 →
94Routes 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 →
57YearsYears 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 →

Violet-green Swallow has fallen sharply in Coastal California: down 58% on the route-weighted index since 1970.

Violet-green Swallow In Coastal California Population Forecast

If the recent trend holds, Violet-green Swallow in Coastal California is projected to fall about 50% by 2030 — from 7.3 in 2025 to a central estimate of 3.7 (95% range 0.00–7.5). A 5-year backtest shows a typical error of ±32.4%, with 100% of held-out values landing inside the 95% band.

-50%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 →
3.7Projected 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 →
0.00–7.595% 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 →
±32.4%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, Violet-green Swallow in Coastal California is projected to fall about 50% by 2030 — from 7.3 in 2025 to a central estimate of 3.7 (95% range 0.00–7.5). A 5-year backtest shows a typical error of ±32.4%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20264.30.488.1
20274.10.337.9
20284.00.187.8
20293.80.037.6
20303.70.007.5

Routes In Coastal California

Routes recording Violet-green Swallow 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 →
ArvinCALIFORNIA1721988
Big BearCALIFORNIA821986
Lake HemetCALIFORNIA631986
RiovistaCALIFORNIA572022
FairfaxCALIFORNIA472024
ValyermoCALIFORNIA412019
Carmel ValCALIFORNIA402025
LockwoodCALIFORNIA402025
Tres Pinos 2CALIFORNIA392011
FallsvaleCALIFORNIA331981
CoyoteCALIFORNIA272025
White RiverCALIFORNIA241992
Point ReyesCALIFORNIA222025
GlennCALIFORNIA221991
Glen EllenCALIFORNIA222004
GreenfieldCALIFORNIA202025
Mesa GrandeCALIFORNIA172025
AdelaidaCALIFORNIA172025
Gold HillCALIFORNIA162025
Cal Hot SpgsCALIFORNIA162019
Santa YnezCALIFORNIA152019
MoragaCALIFORNIA132025
Glen Ellen 3CALIFORNIA122025
AuburnCALIFORNIA111980
AthloneCALIFORNIA111980

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