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

Generalists In Illinois

All statesIllinois

12 species in this guild. As a group they are -69%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 →

Generalists as a group have fallen sharply in Illinois, down 69% since 1968.

Generalists In Illinois Population Forecast

If the recent trend holds, Generalists in Illinois is projected to fall about 50% by 2030 — from 22 in 2025 to a central estimate of 11 (95% range 2.1–19). A 5-year backtest shows a typical error of ±32.4%, with 80% of held-out values landing inside the 95% band.

-50%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 →
11Projected 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 →
2.1–1995% 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 →
±32.4%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, Generalists in Illinois is projected to fall about 50% by 2030 — from 22 in 2025 to a central estimate of 11 (95% range 2.1–19). A 5-year backtest shows a typical error of ±32.4%, with 80% 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 →
2026145.623
2027134.722
2028133.921
2029123.020
2030112.119

Member Species In Illinois

Generalists 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 →
House SparrowPasseridae-81%
Common GrackleIcteridae-74%
Rock PigeonColumbidae-73%
Northern MockingbirdMimidae-48%
European StarlingSturnidae-40%
American CrowCorvidae+13%
Mourning DoveColumbidae+13%
Brown-headed CowbirdIcteridae+156%
Eurasian Tree SparrowPasseridae+332%
Fish CrowCorvidae12×
House FinchFringillidae30×
Eurasian Collared-DoveColumbidae38×

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