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Species · Illinois · BBS 2025 Release · 1966–2024

Savannah Sparrow Population Trend in Illinois

All statesGrassland birds

Savannah Sparrow in Illinois has collapsed: down 86% on the route-weighted index since 1968.

-86%Since 1968TrendPercent 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 →
75Routes 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 Savannah 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 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 →

Savannah Sparrow has collapsed in Illinois: down 86% on the route-weighted index since 1968.

Savannah Sparrow Population Forecast in Illinois

If the recent trend holds, Savannah Sparrow in Illinois is projected to fall about 66% by 2029 — from 0.19 in 2024 to a central estimate of 0.06 (95% range 0.00–1.0). A 5-year backtest shows a typical error of ±26.6%, with 100% of held-out values landing inside the 95% band.

-66%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 →
0.06Projected 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 →
0.00–1.095% 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 →
±26.6%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 →
19662029
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 →
20250.200.001.2
20260.170.001.1
20270.130.001.1
20280.100.001.1
20290.060.001.0

Savannah Sparrow Survey Routes in Illinois

Routes recording Savannah 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 →
Clayton2420192001
Harristown920192018
Alden720232019
Olney619701970
Troy Grove620121994
Robinson520232022
Geneseo420211979
Caledonia420241993
Sheffield320161973
New Lenox320191967
Yale320242024
Brownville320062005
Cherry Val 2320042004
Mill Creek220231966
Holcomb220241971
Cherry Val220011972
Putnam220241967
Buda220031982
Essex220141969
Cameron220132011
Fairbury220051977
Pontiac219931978
Janesville220222001
Humboldt220021988
Jamestown220211984

Savannah Sparrow Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutdelawareidahoindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooregonpennsylvaniarhode-islandsouth-dakotatennesseeutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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