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Species · Illinois · BBS 2025 Release · 1966–2024

Gray Partridge Population Trend in Illinois

All statesGeneralists

Gray Partridge in Illinois has collapsed: down 96% on the route-weighted index since 1971.

-96%Since 1971TrendPercent 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 →
11Routes 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 →
24YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Gray Partridge Trends in IllinoisNotable 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 →

Gray Partridge has collapsed in Illinois: down 96% on the route-weighted index since 1971.

Gray Partridge Population Forecast in Illinois

If the recent trend holds, Gray Partridge in Illinois is projected to stay roughly flat through 2015, near 0.00 (95% range 0.00–0.50). A 5-year backtest shows a typical error of ±1009.9%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2015TrendPercent 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 →
0.00Projected 2015 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5095% 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 →
±1009.9%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, Gray Partridge in Illinois is projected to stay roughly flat through 2015, near 0.00 (95% range 0.00–0.50). A 5-year backtest shows a typical error of ±1009.9%, with 100% of held-out values landing inside the 95% band.19662015
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 →
20110.000.000.50
20120.000.000.50
20130.000.000.50
20140.000.000.50
20150.000.000.50

Gray Partridge Survey Routes in Illinois

Routes recording Gray Partridge in Illinois.
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 →
Mill Creek419881966
Guilford219891985
Holcomb219931971
Cherry Val219921972
Troy Grove219951995
Seneca219991993
Atkinson219871987
Geneseo219901988
Sheffield119911988
Compton119921972
Newark120101970

Gray Partridge Population Trend in Other States

idahoindianaiowaminnesotamontananebraskanevadanew-yorknorth-dakotaoregonsouth-dakotautahwashingtonwisconsinwyoming

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