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Species · Illinois · BBS 2026 Release · 1966–2025

Grasshopper Sparrow Population Trend in Illinois

All statesGrassland birds

Grasshopper Sparrow in Illinois has collapsed: down 94% on the route-weighted index since 1968.

-94%Since 1968TrendPercent 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 →
99Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Grasshopper Sparrow 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 →

Grasshopper Sparrow has collapsed in Illinois: down 94% on the route-weighted index since 1968.

Grasshopper Sparrow Population Forecast in Illinois

If the recent trend holds, Grasshopper Sparrow in Illinois is projected to fall about 100% by 2030 — from 0.37 in 2025 to a central estimate of 0.00 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±45.9%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–1.795% 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 →
±45.9%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, Grasshopper Sparrow in Illinois is projected to fall about 100% by 2030 — from 0.37 in 2025 to a central estimate of 0.00 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±45.9%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20260.190.001.8
20270.110.001.8
20280.030.001.7
20290.000.001.7
20300.000.001.7

Grasshopper Sparrow Survey Routes in Illinois

Routes recording Grasshopper Sparrow 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 →
Bluff Spgs520251967
New Lenox419901966
Martinsville420131976
Shannon419941993
York420251993
Brownville420251993
Cave In Rock420171997
Lake Galena420212002
Royalton420242001
Karnak420152001
Guilford320111968
Mackinaw320251966
Fairbury320241976
Beaucoup320211972
Greenview320251993
Cherry Val219961976
Putnam220191972
Essex220011969
Chandlervill220251971
Terre Haute220251966
Monica220111973
Melrose219991973
Concord220111967
Pawnee220181967
Humboldt220081970

Grasshopper Sparrow Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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