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

Northern Rough-winged Swallow In Sierra Nevada

All regionsSierra NevadaAerial insectivores

Northern Rough-winged Swallow in Sierra Nevada has fallen sharply: down 75% on the route-weighted index since 1972.

-75%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 →
24Routes 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 →

Northern Rough-winged Swallow has fallen sharply in Sierra Nevada: down 75% on the route-weighted index since 1972.

Northern Rough-winged Swallow In Sierra Nevada Population Forecast

If the recent trend holds, Northern Rough-winged Swallow in Sierra Nevada is projected to fall about 51% by 2029 — from 0.26 in 2024 to a central estimate of 0.13 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±94.6%, with 100% of held-out values landing inside the 95% band.

-51%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 →
0.13Projected 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 →
0.00–1.295% 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 →
±94.6%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, Northern Rough-winged Swallow in Sierra Nevada is projected to fall about 51% by 2029 — from 0.26 in 2024 to a central estimate of 0.13 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±94.6%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20250.190.001.3
20260.180.001.2
20270.160.001.2
20280.150.001.2
20290.130.001.2

Routes In Sierra Nevada

Routes recording Northern Rough-winged 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 →
Bass LakeCALIFORNIA42007
GeneseeCALIFORNIA32024
CoultervilleCALIFORNIA32012
KernvilleCALIFORNIA32008
DardanelleCALIFORNIA21973
JohnsvilleCALIFORNIA22014
Silver CityCALIFORNIA21994
SattleyCALIFORNIA22012
Butte MeadowCALIFORNIA21997
PaxtonCALIFORNIA22024
Forest HillCALIFORNIA22019
Eagle LakeCALIFORNIA12013
Cottage SpgsCALIFORNIA11973
WoodfordsCALIFORNIA12009
Greenhorn MtCALIFORNIA11974
Kings CanyonCALIFORNIA12005
Tuolumne GroveCALIFORNIA12011
Higgins CornCALIFORNIA12013
DownievilleCALIFORNIA12019
RivertonCALIFORNIA12019
Hat CreekCALIFORNIA12015
LakeshoreCALIFORNIA11997
Little TruckeeCALIFORNIA12002
PlacervilleCALIFORNIA12011

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