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

Brown-headed Cowbird In Sierra Nevada

All regionsSierra NevadaGeneralists

Brown-headed Cowbird in Sierra Nevada has declined: down 30% on the route-weighted index since 1970.

-30%Since 1970
39Routes In Region
56Years

Notable Signals

No notable trend signals for Brown-headed Cowbird in Sierra Nevada. See the full index history below.

Forecast

If the recent trend holds, Brown-headed Cowbird in Sierra Nevada is projected to fall about 33% by 2029 — from 4.9 in 2024 to a central estimate of 3.3 (95% range 1.3–5.4). A 5-year backtest shows a typical error of ±28.7%, with 100% of held-out values landing inside the 95% band.

-33%Change by 2029
3.3Projected 2029 index
1.3–5.495% range
±28.7%Backtest error
19682029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected index95% low95% high
20253.41.45.4
20263.41.45.4
20273.41.45.4
20283.41.35.4
20293.31.35.4

Routes In Sierra Nevada

Routes recording Brown-headed Cowbird in Sierra Nevada.
ChilcootCALIFORNIA222024
SattleyCALIFORNIA192024
GeneseeCALIFORNIA142024
Eagle LakeCALIFORNIA112024
Bass LakeCALIFORNIA112019
Last ChanceCALIFORNIA82019
Tahoe NfCALIFORNIA61994
Greenhorn MtCALIFORNIA52008
Higgins CornCALIFORNIA52024
WawonaCALIFORNIA52024
Butte MeadowCALIFORNIA42014
GoumazCALIFORNIA42011
Silver CityCALIFORNIA32013
Tuolumne GroveCALIFORNIA32024
RivertonCALIFORNIA32012
Hat CreekCALIFORNIA32016
PaxtonCALIFORNIA32024
Pollock PinesCALIFORNIA32024
KernvilleCALIFORNIA32008
DownievilleCALIFORNIA22024
LakeshoreCALIFORNIA22024
PlacervilleCALIFORNIA22024
CoultervilleCALIFORNIA22018
StrawberryCALIFORNIA22010
Lassen ParkCALIFORNIA11986

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