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

Grassland Birds In Illinois

All statesIllinois

13 species in this guild. As a group they are -66%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 66% since 1968.

Grassland Birds In Illinois Population Forecast

If the recent trend holds, Grassland birds in Illinois is projected to fall about 46% by 2030 — from 5.3 in 2025 to a central estimate of 2.8 (95% range 0.00–6.5). A 5-year backtest shows a typical error of ±33.3%, with 100% of held-out values landing inside the 95% band.

-46%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 →
2.8Projected 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 →
0.00–6.595% 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 →
±33.3%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 46% by 2030 — from 5.3 in 2025 to a central estimate of 2.8 (95% range 0.00–6.5). A 5-year backtest shows a typical error of ±33.3%, 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 →
20263.40.007.0
20273.20.006.9
20283.10.006.8
20293.00.006.6
20302.80.006.5

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%
Loggerhead ShrikeLaniidae-97%
BobolinkIcteridae-97%
Grasshopper SparrowPasserellidae-94%
Savannah SparrowPasserellidae-84%
Horned LarkAlaudidae-71%
Lark SparrowPasserellidae-71%
Eastern MeadowlarkIcteridae-70%
Sedge WrenTroglodytidae-57%
Upland SandpiperScolopacidae-50%
Vesper SparrowPasserellidae-43%
DickcisselCardinalidae-39%
Henslow's SparrowPasserellidae+48%

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