BirdAnalyst
Species · Idaho · BBS 2026 Release · 1966–2025

Fox Sparrow Population Trend in Idaho

All statesForest birds

Fox Sparrow in Idaho has surged: up 326% on the route-weighted index since 1977.

+326%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 →
33Routes 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 →
50YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Fox Sparrow 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 →

Fox Sparrow has surged in Idaho: up 326% on the route-weighted index since 1977.

Fox Sparrow Population Forecast in Idaho

If the recent trend holds, Fox Sparrow in Idaho is projected to fall about 33% by 2030 — from 2.1 in 2025 to a central estimate of 1.4 (95% range 0.49–2.3). A 5-year backtest shows a typical error of ±29.8%, with 60% of held-out values landing inside the 95% band.

-33%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 →
1.4Projected 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 →
0.49–2.395% 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 →
±29.8%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, Fox Sparrow in Idaho is projected to fall about 33% by 2030 — from 2.1 in 2025 to a central estimate of 1.4 (95% range 0.49–2.3). A 5-year backtest shows a typical error of ±29.8%, with 60% of held-out values landing inside the 95% band.19712030
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 →
20261.30.442.2
20271.30.452.2
20281.40.462.3
20291.40.482.3
20301.40.492.3

Fox Sparrow Survey Routes in Idaho

Routes recording Fox Sparrow 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 →
Magic Mtn2620251992
Avery1220251979
Lolo Pass920191992
Pierce720071994
Silver City720251993
Sunbeam520251994
Centerville420251982
Challis320251977
Baldy Mountain320162013
Sawtooth City 2320252015
Burgdorf320251988
Cascade219841983
Cape Horn220222021
Rochat Divde220251993
Squirrel220051971
Marble Creek220251988
Yellow Pine220161990
Featherville220251990
Bates220051996
Almo220252014
Sawtooth Cty220142011
Mivoden120181977
Grangeville120251986
Golden120141994
N Fork Cda R120032003

Fox Sparrow Population Trend in Other States

alaskacaliforniacoloradomainemontananevadaoregonutahwashingtonwyoming

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