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

Yellow-billed Cuckoo Population Trend in Connecticut

All statesGeneralists

Yellow-billed Cuckoo in Connecticut has fallen sharply: down 72% on the route-weighted index since 1968.

-72%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 →
20Routes 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 →
53YearsYears 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 ConnecticutNotable 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 →

Yellow-billed Cuckoo has fallen sharply in Connecticut: down 72% on the route-weighted index since 1968.

Yellow-billed Cuckoo Population Forecast in Connecticut

If the recent trend holds, Yellow-billed Cuckoo in Connecticut is projected to rise about 173% by 2029 — from 0.11 in 2024 to a central estimate of 0.30 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±76.2%, with 100% of held-out values landing inside the 95% band.

+173%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 →
0.30Projected 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 →
0.00–1.595% 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 →
±76.2%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, Yellow-billed Cuckoo in Connecticut is projected to rise about 173% by 2029 — from 0.11 in 2024 to a central estimate of 0.30 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±76.2%, 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 →
20250.340.001.6
20260.330.001.6
20270.320.001.5
20280.310.001.5
20290.300.001.5

Yellow-billed Cuckoo Survey Routes in Connecticut

Routes recording Yellow-billed Cuckoo in Connecticut.
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 →
Willimantic720181967
Woodstock520071971
Warren 2520212019
Buckingham320161966
Woodstock 2320192017
Mystic220191973
No Woodbury220231967
Danbury220141968
Mid Haddam220191973
New Hartford219811973
Granby220222005
E Hartland119851971
Uncasville120241973
Westbrook120151978
Sherman120181972
Greenwich120071967
Warren119881972
Long Hill120151972
Southington120181973
New Hartford120221996

Yellow-billed Cuckoo Population Trend in Other States

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

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