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

Northern Harrier In Sierra Nevada

All regionsSierra NevadaGeneralists

Northern Harrier in Sierra Nevada has held roughly steady: up 10% on the route-weighted index since 1998.

+10%Since 1998TrendPercent 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 →
9Routes 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 →
18YearsYears 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 →

No notable trend signals for Northern Harrier in Sierra Nevada. See the full index history below.

Forecast

If the recent trend holds, Northern Harrier in Sierra Nevada is projected to fall about 11% by 2029 — from 0.05 in 2024 to a central estimate of 0.05 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±31.1%, with 100% of held-out values landing inside the 95% band.

-11%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 →
0.05Projected 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 →
0.00–0.1095% 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 →
±31.1%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, Northern Harrier in Sierra Nevada is projected to fall about 11% by 2029 — from 0.05 in 2024 to a central estimate of 0.05 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±31.1%, with 100% of held-out values landing inside the 95% band.19902029
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 →
20250.050.000.10
20260.050.000.10
20270.050.000.10
20280.050.000.10
20290.050.000.10

Routes In Sierra Nevada

Routes recording Northern Harrier 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 →
GoumazCALIFORNIA22010
Last ChanceCALIFORNIA22015
Eagle LakeCALIFORNIA12024
WoodfordsCALIFORNIA11990
SattleyCALIFORNIA12017
GeneseeCALIFORNIA12005
Hat CreekCALIFORNIA12000
Little TruckeeCALIFORNIA12014
CrestviewCALIFORNIA12016

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