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Species · Illinois · BBS 2026 Release · 1966–2025

Yellow-billed Cuckoo Population Trend in Illinois

All statesForest birds

Yellow-billed Cuckoo in Illinois has declined: down 39% on the route-weighted index since 1968.

-39%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 →
100Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Yellow-billed Cuckoo 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 →

No notable trend signals for Yellow-billed Cuckoo in Illinois. See the full index history below.

Yellow-billed Cuckoo Population Forecast in Illinois

If the recent trend holds, Yellow-billed Cuckoo in Illinois is projected to stay roughly flat through 2030, near 1.4 (95% range 0.00–3.7). A 5-year backtest shows a typical error of ±22.8%, with 100% of held-out values landing inside the 95% band.

-1%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 →
1.4Projected 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 →
0.00–3.795% 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 →
±22.8%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, Yellow-billed Cuckoo in Illinois is projected to stay roughly flat through 2030, near 1.4 (95% range 0.00–3.7). A 5-year backtest shows a typical error of ±22.8%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20261.60.003.9
20271.50.003.9
20281.50.003.8
20291.40.003.8
20301.40.003.7

Yellow-billed Cuckoo Survey Routes in Illinois

Routes recording Yellow-billed Cuckoo 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 →
Belleview1220251966
Pulaski1220251970
Athens1120251995
Beaverdam Lk920231970
Cave In Rock820241993
Sandusky620231993
Karnak620242001
Putnam520221967
Bluff Spgs520251967
Belknap520251970
Yale520241993
Kell520252001
St Morgan420221967
Bremen420251969
Camp Point420251993
Lake Summerset420192003
Clayton420212001
Grape Creek420252002
Royalton420252001
Sheffield320221966
Terre Haute320251966
Milford320221966
Humboldt320211970
Martinsville320251970
Birds320241976

Yellow-billed Cuckoo Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

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