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

Wetland Birds In Illinois

All statesIllinois

16 species in this guild. As a group they are -51%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 →

Wetland birds as a group have fallen sharply in Illinois, down 51% since 1968.

Wetland Birds In Illinois Population Forecast

If the recent trend holds, Wetland birds in Illinois is projected to fall about 16% by 2030 — from 11 in 2025 to a central estimate of 9.1 (95% range 2.8–15). A 5-year backtest shows a typical error of ±12.3%, with 100% of held-out values landing inside the 95% band.

-16%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 →
9.1Projected 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 →
2.8–1595% 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 →
±12.3%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, Wetland birds in Illinois is projected to fall about 16% by 2030 — from 11 in 2025 to a central estimate of 9.1 (95% range 2.8–15). A 5-year backtest shows a typical error of ±12.3%, 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 →
20269.93.616
20279.73.416
20289.53.216
20299.33.016
20309.12.815

Member Species In Illinois

Wetland 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 →
American CootRallidae-96%
Western Cattle-EgretArdeidae-94%
Little Blue HeronArdeidae-86%
Pied-billed GrebePodicipedidae-77%
Yellow-crowned Night HeronArdeidae-69%
Swamp SparrowPasserellidae-43%
Black-crowned Night HeronArdeidae-41%
Green HeronArdeidae-26%
Red-winged BlackbirdIcteridae-23%
Sandhill CraneGruidae-17%
Belted KingfisherAlcedinidae-8%
Great EgretArdeidae+100%
Herring GullLaridae+173%
Great Blue HeronArdeidae+231%
Ring-billed GullLaridae+395%
Double-crested CormorantPhalacrocoracidae14×

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