BirdAnalyst
Species · BCR 15 · BBS 2026 Release · 1966–2025

Black-billed Magpie In Sierra Nevada

All regionsSierra NevadaGeneralists

Black-billed Magpie in Sierra Nevada has fallen sharply: down 64% on the route-weighted index since 1974.

-64%Since 1974TrendPercent 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 →
7Routes 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 →
52YearsYears 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 →

Black-billed Magpie has fallen sharply in Sierra Nevada: down 64% on the route-weighted index since 1974.

Black-billed Magpie In Sierra Nevada Population Forecast

If the recent trend holds, Black-billed Magpie in Sierra Nevada is projected to rise about 207% by 2030 — from 0.28 in 2025 to a central estimate of 0.85 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±438.2%, with 100% of held-out values landing inside the 95% band.

+207%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 →
0.85Projected 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 →
0.00–1.995% 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 →
±438.2%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, Black-billed Magpie in Sierra Nevada is projected to rise about 207% by 2030 — from 0.28 in 2025 to a central estimate of 0.85 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±438.2%, 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 →
20260.840.001.8
20270.850.001.8
20280.850.001.8
20290.850.001.9
20300.850.001.9

Routes In Sierra Nevada

Routes recording Black-billed Magpie 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 →
SattleyCALIFORNIA52025
PaxtonCALIFORNIA42024
DardanelleCALIFORNIA22014
GeneseeCALIFORNIA22024
JohnsvilleCALIFORNIA11978
ChilcootCALIFORNIA12023
Last ChanceCALIFORNIA12019

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