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Species · Illinois · BBS 2025 Release · 1966–2024

Horned Lark Population Trend in Illinois

All statesGrassland birds

Horned Lark 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 →
102Routes 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 Horned Lark 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 →

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

Horned Lark Population Forecast in Illinois

If the recent trend holds, Horned Lark in Illinois is projected to fall about 16% by 2029 — from 10 in 2024 to a central estimate of 8.5 (95% range 0.00–24). A 5-year backtest shows a typical error of ±32.2%, with 100% of held-out values landing inside the 95% band.

-16%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 →
8.5Projected 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 →
0.00–2495% 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 →
±32.2%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, Horned Lark in Illinois is projected to fall about 16% by 2029 — from 10 in 2024 to a central estimate of 8.5 (95% range 0.00–24). A 5-year backtest shows a typical error of ±32.2%, 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 →
2025110.0026
2026100.0025
20279.60.0025
20289.10.0024
20298.50.0024

Horned Lark Survey Routes in Illinois

Routes recording Horned Lark 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 →
Melrose6919991973
Marshall5920242001
Bradbury5520241970
Alden3520232019
York3320241993
Beaucoup3120241971
Martinsville2920241970
Fairdale2820242019
Stillwell2720231971
Monticello2520241976
Dudleyville2320242001
Janesville2120241972
Sterling2120232001
Mill Creek2020241966
Fairland2020241967
Jamestown2020241966
Grape Creek1920242001
Williamsfld1820241971
Mascoutah Lk1620241967
St Morgan1620221967
Yale1620241993
Union1620172001
Kell1620242001
Robinson1520231970
Bartonville1420241973

Horned Lark Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawaregeorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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