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Species · Illinois · BBS 2025 Release · 1966–2024

Carolina Wren Population Trend in Illinois

All statesForest birds

Carolina Wren in Illinois has surged: up 196% on the route-weighted index since 1968.

+196%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 →
86Routes 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 Carolina Wren 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 →

Carolina Wren has surged in Illinois: up 196% on the route-weighted index since 1968.

Carolina Wren Population Forecast in Illinois

If the recent trend holds, Carolina Wren in Illinois is projected to fall about 15% by 2029 — from 5.1 in 2024 to a central estimate of 4.3 (95% range 2.0–6.6). A 5-year backtest shows a typical error of ±97.2%, with 60% of held-out values landing inside the 95% band.

-15%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 →
4.3Projected 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 →
2.0–6.695% 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 →
±97.2%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, Carolina Wren in Illinois is projected to fall about 15% by 2029 — from 5.1 in 2024 to a central estimate of 4.3 (95% range 2.0–6.6). A 5-year backtest shows a typical error of ±97.2%, with 60% of held-out values landing inside the 95% band.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 →
20254.11.86.4
20264.11.86.5
20274.21.96.5
20284.21.96.6
20294.32.06.6

Carolina Wren Survey Routes in Illinois

Routes recording Carolina Wren 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 →
Cave In Rock3720241993
Pulaski3120241970
Belknap2520241970
Royalton2520242001
Sandusky2320231993
Brownville2220241993
Belleview1820241966
Eldred1720191993
York1520241993
Bradbury1420241970
Mt Vernon1420241971
Karnak1420242001
Bremen1320241969
Mascoutah Lk1220241969
Brnt Prairie1220241976
St Morgan1120221967
Beaverdam Lk1120231970
Delwood1020241971
Grape Creek920242002
Concord820241967
Marshall820242003
Athens820241995
Darmstadt720241993
Olney620241968
Yale620241994

Carolina Wren Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsin

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