BirdAnalyst
Species · Illinois · BBS 2025 Release · 1966–2024

Yellow-billed Cuckoo Population Trend in Illinois

All statesGeneralists

Yellow-billed Cuckoo in Illinois has declined: down 29% on the route-weighted index since 1968.

-29%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 →
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 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 fall about 43% by 2029 — from 2.5 in 2024 to a central estimate of 1.4 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±25.1%, with 100% of held-out values landing inside the 95% band.

-43%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 →
0.00–3.895% 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 →
±25.1%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 fall about 43% by 2029 — from 2.5 in 2024 to a central estimate of 1.4 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±25.1%, with 100% 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 →
20251.70.004.0
20261.60.004.0
20271.50.003.9
20281.50.003.8
20291.40.003.8

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 →
Belknap2120241970
Belleview2020241966
Pulaski1520241970
Mascoutah Lk1420241967
Delwood1120241970
Royalton1020242001
Beaverdam Lk920231970
Cave In Rock820241993
Duncan Mills720241993
Eldred720211993
Eubanks720242002
Mt Vernon620241971
York620241993
Sandusky620231993
Karnak620242001
Putnam520221967
Bluff Spgs520241967
Bremen520241969
Yale520241993
Bradbury420241970
St Morgan420221967
Lake Summerset420192003
Clayton420212001
Kell420242001
Sheffield320221966

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 2026-05-22.