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

Black-billed Cuckoo Population Trend in Delaware

All statesGeneralists

Black-billed Cuckoo in Delaware has fallen sharply: down 57% on the route-weighted index since 1969.

-57%Since 1969TrendPercent 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 →
12Routes 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 →
26YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-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 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 →

Black-billed Cuckoo has fallen sharply in Delaware: down 57% on the route-weighted index since 1969.

Black-billed Cuckoo Population Forecast in Delaware

If the recent trend holds, Black-billed Cuckoo in Delaware is projected to fall about 100% by 2024 — from 0.14 in 2019 to a central estimate of 0.00 (95% range 0.00–0.63). A 5-year backtest shows a typical error of ±122.3%, with 100% of held-out values landing inside the 95% band.

-100%Change by 2024TrendPercent 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 →
0.00Projected 2024 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.6395% 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 →
±122.3%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, Black-billed Cuckoo in Delaware is projected to fall about 100% by 2024 — from 0.14 in 2019 to a central estimate of 0.00 (95% range 0.00–0.63). A 5-year backtest shows a typical error of ±122.3%, with 100% of held-out values landing inside the 95% band.19662024
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 →
20200.000.000.63
20210.000.000.63
20220.000.000.63
20230.000.000.63
20240.000.000.63

Black-billed Cuckoo Survey Routes in Delaware

Routes recording Black-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 →
Lowes Xrds519731967
Georgetown319931993
Dover219791967
Frankford220081973
Mt Pleasant119871967
Wilmington119881969
Harrington119951970
Frederica119801971
Holleyville120041969
Blackbird120051994
Milton119851966
Pepperbox 2120192019

Black-billed Cuckoo Population Trend in Other States

alabamaarkansascoloradoconnecticutgeorgiaidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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