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

Yellow-billed Cuckoo Population Trend in Delaware

All statesGeneralists

Yellow-billed Cuckoo in Delaware has surged: up 152% on the route-weighted index since 1968.

+152%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 →
17Routes 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 DelawareNotable 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 →

Yellow-billed Cuckoo has surged in Delaware: up 152% on the route-weighted index since 1968.

Yellow-billed Cuckoo Population Forecast in Delaware

If the recent trend holds, Yellow-billed Cuckoo in Delaware is projected to fall about 45% by 2029 — from 5.4 in 2024 to a central estimate of 2.9 (95% range 0.00–7.2). A 5-year backtest shows a typical error of ±66.9%, with 40% of held-out values landing inside the 95% band.

-45%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 →
2.9Projected 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 →
0.00–7.295% 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 →
±66.9%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 Delaware is projected to fall about 45% by 2029 — from 5.4 in 2024 to a central estimate of 2.9 (95% range 0.00–7.2). A 5-year backtest shows a typical error of ±66.9%, with 40% 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 →
20252.90.007.2
20262.90.007.2
20272.90.007.2
20282.90.007.2
20292.90.007.2

Yellow-billed Cuckoo Survey Routes in Delaware

Routes recording Yellow-billed Cuckoo in Delaware.
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 →
Pepperbox 21320242017
Blackbird1120241994
Milton 21120172017
Lowes Xrds919911966
Holleyville 2920192006
Holleyville720041966
Harrington420221966
Georgetown420221992
Millsboro320242017
Frankford220121966
Milton220141967
Mt Pleasant120051966
Wilmington120111966
Frederica120141966
Dover119861967
Bethany Bch119901966
Pepperbox120161998

Yellow-billed Cuckoo Population Trend in Other States

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

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