BirdAnalyst
Species · Idaho · BBS 2025 Release · 1966–2024

Ferruginous Hawk Population Trend in Idaho

All statesGeneralists

Ferruginous Hawk in Idaho has surged: up 675% on the route-weighted index since 1977.

+675%Since 1977TrendPercent 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 →
26Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
44YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Ferruginous Hawk Trends in IdahoNotable 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 increasecomputed 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 →

Ferruginous Hawk has surged in Idaho: up 675% on the route-weighted index since 1977.

Ferruginous Hawk Population Forecast in Idaho

If the recent trend holds, Ferruginous Hawk in Idaho is projected to fall about 28% by 2029 — from 0.72 in 2024 to a central estimate of 0.52 (95% range 0.11–0.92). A 5-year backtest shows a typical error of ±126.8%, with 40% of held-out values landing inside the 95% band.

-28%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 →
0.52Projected 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 →
0.11–0.9295% 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 →
±126.8%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, Ferruginous Hawk in Idaho is projected to fall about 28% by 2029 — from 0.72 in 2024 to a central estimate of 0.52 (95% range 0.11–0.92). A 5-year backtest shows a typical error of ±126.8%, with 40% of held-out values landing inside the 95% band.19732029
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 →
20250.490.090.90
20260.500.090.90
20270.500.100.91
20280.510.110.92
20290.520.110.92

Ferruginous Hawk Survey Routes in Idaho

Routes recording Ferruginous Hawk in Idaho.
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 →
Dubois920241974
Silver City420022002
Lost River320241988
Cedar Hill320141998
Kyle Canyon220241985
Circular Bu220241987
Acequia220122012
Mud Lake220212015
Almo220211988
Blackft Res119921992
Gifford119731973
Twin Buttes120231985
Tractor Flat120241988
Leadore120241994
Squirrel119771977
Blacks Creek119891989
Craters119991979
Springfield119861980
Triangle120041994
Crane Creek120141988
Iron Springs120212001
Picabo120182018
Carey120012001
Bates120001989
Daniels Res120141993

Ferruginous Hawk Population Trend in Other States

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