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

Lark Sparrow Population Trend in Illinois

All statesGrassland birds

Lark Sparrow in Illinois has fallen sharply: down 71% on the route-weighted index since 1968.

-71%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 →
67Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Lark 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 →

Lark Sparrow has fallen sharply in Illinois: down 71% on the route-weighted index since 1968.

Lark Sparrow Population Forecast in Illinois

If the recent trend holds, Lark Sparrow in Illinois is projected to fall about 63% by 2030 — from 0.19 in 2025 to a central estimate of 0.07 (95% range 0.00–0.47). A 5-year backtest shows a typical error of ±52%, with 100% of held-out values landing inside the 95% band.

-63%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 →
0.07Projected 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 →
0.00–0.4795% 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 →
±52%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, Lark Sparrow in Illinois is projected to fall about 63% by 2030 — from 0.19 in 2025 to a central estimate of 0.07 (95% range 0.00–0.47). A 5-year backtest shows a typical error of ±52%, 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 →
20260.090.000.49
20270.080.000.48
20280.080.000.48
20290.070.000.47
20300.070.000.47

Lark Sparrow Survey Routes in Illinois

Routes recording Lark 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 →
Clarksdale419711971
Milford320232023
Athensville320211985
Columbia320231967
Putnam220241967
Gulfport220252002
Stillwell220231976
Mackinaw219851967
Bradbury219961996
Martinsville220251970
Mt Vernon220021992
Royalton220232023
Camp Point220251993
Eldred220151997
Athens120091996
Atkinson120111999
Geneseo119901968
Sheffield120191966
Buda120151994
Payson120252002
Wayne120112011
Newark120112011
New Lenox120152015
Chandlervill120041975
Terre Haute120251966

Lark Sparrow Population Trend in Other States

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