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

Violet-green Swallow In Sierra Nevada

All regionsSierra NevadaAerial insectivores

Violet-green Swallow in Sierra Nevada has collapsed: down 81% on the route-weighted index since 1972.

-81%Since 1972TrendPercent 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 →
29Routes 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 →
54YearsYears 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 collapsed in Sierra Nevada: down 81% on the route-weighted index since 1972.

Violet-green Swallow In Sierra Nevada Population Forecast

If the recent trend holds, Violet-green Swallow in Sierra Nevada is projected to fall about 100% by 2029 — from 1.1 in 2024 to a central estimate of 0.00 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±60.1%, 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 →
0.00–2.995% 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 →
±60.1%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 Sierra Nevada is projected to fall about 100% by 2029 — from 1.1 in 2024 to a central estimate of 0.00 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±60.1%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.210.003.1
20260.130.003.1
20270.060.003.0
20280.000.002.9
20290.000.002.9

Routes In Sierra Nevada

Routes recording Violet-green Swallow 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 →
Forest Hill 2CALIFORNIA112005
SattleyCALIFORNIA61994
PaxtonCALIFORNIA62024
WoodfordsCALIFORNIA52024
ChilcootCALIFORNIA52024
WestvilleCALIFORNIA42022
Bass LakeCALIFORNIA42019
Silver CityCALIFORNIA42013
Kings CanyonCALIFORNIA42024
Lassen ParkCALIFORNIA21986
DownievilleCALIFORNIA21996
Hat CreekCALIFORNIA22007
Forest HillCALIFORNIA22021
Pine MountainCALIFORNIA22017
Eagle LakeCALIFORNIA12018
Cottage SpgsCALIFORNIA11975
DardanelleCALIFORNIA12014
Greenhorn MtCALIFORNIA12008
Tuolumne GroveCALIFORNIA12024
Butte MeadowCALIFORNIA11988
GeneseeCALIFORNIA12019
Higgins CornCALIFORNIA11991
RivertonCALIFORNIA11992
LakeshoreCALIFORNIA12002
GoumazCALIFORNIA12002

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