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Species · Illinois · BBS 2025 Release · 1966–2024

Eurasian Tree Sparrow Population Trend in Illinois

All statesGeneralists

Eurasian Tree Sparrow in Illinois has surged: up 294% on the route-weighted index since 1969.

+294%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 →
45Routes 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 →
57YearsYears 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 294% 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 17% by 2029 — from 1.7 in 2024 to a central estimate of 1.4 (95% range 0.65–2.2). A 5-year backtest shows a typical error of ±31.5%, with 80% of held-out values landing inside the 95% band.

-17%Change by 2029TrendPercent 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 →
1.4Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.65–2.295% 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 →
±31.5%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 17% by 2029 — from 1.7 in 2024 to a central estimate of 1.4 (95% range 0.65–2.2). A 5-year backtest shows a typical error of ±31.5%, with 80% of held-out values landing inside the 95% band.19672029
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 →
20251.30.562.1
20261.30.582.1
20271.40.602.1
20281.40.622.1
20291.40.652.2

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 →
Cameron1920242005
Terre Haute1420241988
Concord1420231967
Greenview1420241995
Williamsfld1220241973
Buda1020232012
Belleview920241972
Keithsburg920222001
Sherrard920241995
Duncan Mills720241998
Athens620161999
Chandlervill620241971
Mill Creek520232017
Putnam520242021
Clayton520242003
Eubanks520242001
Atkinson420242005
Camp Point420241994
Deer Creek320242019
St Morgan320092002
Dudleyville320242007
Eldred320211993
Payson220242001
Sheffield220162012
Bartonville220242001

Eurasian Tree Sparrow Population Trend in Other States

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