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

Lark Sparrow Population Trend in Illinois

All statesGrassland birds

Lark Sparrow in Illinois has collapsed: down 77% on the route-weighted index since 1968.

-77%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 →
66Routes 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 →
57YearsYears 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 collapsed in Illinois: down 76% 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 59% by 2029 — from 0.16 in 2024 to a central estimate of 0.07 (95% range 0.00–0.47). A 5-year backtest shows a typical error of ±40%, with 100% of held-out values landing inside the 95% band.

-59%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 →
0.07Projected 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 →
0.00–0.4795% 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 →
±40%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 59% by 2029 — from 0.16 in 2024 to a central estimate of 0.07 (95% range 0.00–0.47). A 5-year backtest shows a typical error of ±40%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20250.090.000.49
20260.080.000.48
20270.080.000.48
20280.070.000.47
20290.070.000.47

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
Gulfport320232002
Milford320232023
Athensville320211985
Columbia320231967
Putnam220241967
Stillwell220231976
Terre Haute220241966
Mackinaw219851967
Bradbury219961996
Mt Vernon220021992
Royalton220232023
Camp Point220231993
Eldred220151997
Athens120091996
Atkinson120111999
Geneseo119901968
Sheffield120191966
Buda120151994
Payson120222002
Wayne120112011
Newark120112011
New Lenox120152015
Chandlervill120041975
Cameron120001977

Lark Sparrow Population Trend in Other States

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