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

Grassland Birds In Illinois

All statesIllinois

14 species in this guild. As a group they are -71%Guild trendA mean-index aggregate across the species in this group — the structural direction of the guild, with individual-species noise smoothed out.Full methodology → since 1968.

Guild SignalsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

guild collapsecomputed 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 →

Grassland birds as a group have fallen sharply in Illinois, down 71% since 1968.

Grassland Birds In Illinois Population Forecast

If the recent trend holds, Grassland birds in Illinois is projected to fall about 45% by 2029 — from 4.6 in 2024 to a central estimate of 2.5 (95% range 0.00–6.8). A 5-year backtest shows a typical error of ±35.3%, with 100% of held-out values landing inside the 95% band.

-45%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 →
2.5Projected 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 →
0.00–6.895% 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 →
±35.3%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, Grassland birds in Illinois is projected to fall about 45% by 2029 — from 4.6 in 2024 to a central estimate of 2.5 (95% range 0.00–6.8). A 5-year backtest shows a typical error of ±35.3%, 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 →
20253.30.007.5
20263.10.007.3
20272.90.007.1
20282.70.007.0
20292.50.006.8

Member Species In Illinois

Grassland birds species in Illinois.
TrendPercent 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 →
Western MeadowlarkIcteridae-98%
BobolinkIcteridae-97%
Grasshopper SparrowPasserellidae-94%
Savannah SparrowPasserellidae-86%
Ring-necked PheasantPhasianidae-80%
Northern BobwhiteOdontophoridae-80%
Lark SparrowPasserellidae-77%
Eastern MeadowlarkIcteridae-73%
Horned LarkAlaudidae-71%
Sedge WrenTroglodytidae-55%
Upland SandpiperScolopacidae-47%
Vesper SparrowPasserellidae-44%
DickcisselCardinalidae-37%
Henslow's SparrowPasserellidae+51%

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