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Species · Illinois · BBS 2026 Release · 1966–2025

Eurasian Tree Sparrow Population Trend in Illinois

All statesGeneralists

Eurasian Tree Sparrow in Illinois has surged: up 332% on the route-weighted index since 1969.

+332%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 →
49Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Eurasian Tree Sparrow 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 increasecomputed 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 →

Eurasian Tree Sparrow has surged in Illinois: up 332% on the route-weighted index since 1969.

Eurasian Tree Sparrow Population Forecast in Illinois

If the recent trend holds, Eurasian Tree Sparrow in Illinois is projected to fall about 19% by 2030 — from 1.8 in 2025 to a central estimate of 1.5 (95% range 0.70–2.2). A 5-year backtest shows a typical error of ±37.9%, with 40% of held-out values landing inside the 95% band.

-19%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 →
1.5Projected 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 →
0.70–2.295% 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 →
±37.9%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, Eurasian Tree Sparrow in Illinois is projected to fall about 19% by 2030 — from 1.8 in 2025 to a central estimate of 1.5 (95% range 0.70–2.2). A 5-year backtest shows a typical error of ±37.9%, with 40% of held-out values landing inside the 95% band.19672030
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 →
20261.40.612.1
20271.40.642.1
20281.40.662.2
20291.40.682.2
20301.50.702.2

Eurasian Tree Sparrow Survey Routes in Illinois

Routes recording Eurasian Tree Sparrow 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 →
Cameron1820252005
Payson1620252001
Concord1420231967
Sherrard1420251995
Camp Point1220251994
Buda1020232012
Belleview1020251972
Eubanks1020252001
Terre Haute920251988
Greenview720251995
Mill Creek520232017
Putnam520242021
Williamsfld520251973
Atkinson420242005
Bartonville420252001
Dudleyville420252007
Gulfport320251991
Stillwell320251986
Deer Creek320242019
St Morgan320092002
Le Roy320251999
Eldred320211993
Geneseo220252025
Sheffield220162012
Monica220192007

Eurasian Tree Sparrow Population Trend in Other States

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