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Species · Illinois · BBS 2026 Release · 1966–2025

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 →
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 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 19% by 2030 — from 9.8 in 2025 to a central estimate of 7.9 (95% range 0.00–23). A 5-year backtest shows a typical error of ±25.5%, with 100% of held-out values landing inside the 95% band.

-19%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 →
7.9Projected 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 →
0.00–2395% 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 →
±25.5%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 19% by 2030 — from 9.8 in 2025 to a central estimate of 7.9 (95% range 0.00–23). A 5-year backtest shows a typical error of ±25.5%, 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 →
2026100.0025
20279.60.0025
20289.00.0024
20298.40.0023
20307.90.0023

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 →
York8120251993
Melrose6919991973
Marshall5620252001
Kell3420252001
Bradbury3220251970
Martinsville3120251970
Monticello2720251976
Beaucoup2720251971
Payson2720252000
Jamestown2620251966
Fairland2220251967
Sterling2120232001
Fairbury1720251976
Grape Creek1720252001
St Morgan1620221967
Union1620172001
Rosamond1520251972
Robinson1520231970
Brnt Prairie1420251976
Yale1420251993
Dudleyville1420252001
Buda1320231977
Columbia1320251966
Nilwood1320231993
Fairdale1320252019

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 2026-08-14.