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

Blue-winged Teal Population Trend in Illinois

All statesWaterfowl

Blue-winged Teal in Illinois has collapsed: down 80% on the route-weighted index since 1969.

-80%Since 1969TrendPercent 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 →
32Routes 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 →
36YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Blue-winged Teal 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 →

Blue-winged Teal has collapsed in Illinois: down 80% on the route-weighted index since 1969.

Blue-winged Teal Population Forecast in Illinois

If the recent trend holds, Blue-winged Teal in Illinois is projected to stay roughly flat through 2026, near 0.00 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±834%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2026TrendPercent 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 →
0.00Projected 2026 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.4295% 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 →
±834%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, Blue-winged Teal in Illinois is projected to stay roughly flat through 2026, near 0.00 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±834%, with 100% of held-out values landing inside the 95% band.19672026
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 →
20220.000.000.42
20230.000.000.42
20240.000.000.42
20250.000.000.42
20260.000.000.42

Blue-winged Teal Survey Routes in Illinois

Routes recording Blue-winged Teal 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 →
Itasca1019731973
Belleview819881985
Melrose619901990
Geneseo319751973
Essex319791979
Newark319751970
New Lenox319811967
Olney320132000
Sheffield219741973
Compton219721972
Stillwell219921992
Chandlervill219951973
Terre Haute220042004
Bartonville219731973
Pawnee220021982
Keithsburg220022002
Pulaski219841973
Bremen219731973
Mill Creek119941994
Barrington119921992
Streator119721972
Wayne120211971
Sherburnvill119901968
Monica119931974
Mackinaw120002000

Blue-winged Teal Population Trend in Other States

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