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Species · Connecticut · BBS 2025 Release · 1966–2024

Black-billed Cuckoo Population Trend in Connecticut

All statesGeneralists

Black-billed Cuckoo in Connecticut has fallen sharply: down 71% on the route-weighted index since 1968.

-71%Since 1968
20Routes In State
48Years

Notable Black-billed Cuckoo Trends in Connecticut

long arc declinecomputed index

Black-billed Cuckoo has fallen sharply in Connecticut: down 71% on the route-weighted index since 1968.

Black-billed Cuckoo Population Forecast in Connecticut

If the recent trend holds, Black-billed Cuckoo in Connecticut is projected to fall about 100% by 2028 — from 0.36 in 2023 to a central estimate of 0.00 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±392%, with 100% of held-out values landing inside the 95% band.

-100%Change by 2028
0.00Projected 2028 index
0.00–2.795% range
±392%Backtest error
19662028
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected index95% low95% high
20240.000.002.7
20250.000.002.7
20260.000.002.7
20270.000.002.7
20280.000.002.7

Black-billed Cuckoo Survey Routes in Connecticut

Routes recording Black-billed Cuckoo in Connecticut.
Warren320051972
Mystic220191973
Buckingham220161966
No Woodbury220051967
New Hartford220191994
E Hartland119921966
Uncasville120231973
Woodstock119861968
Westbrook120171970
Willimantic120141967
Sherman120141972
Greenwich119971967
Danbury120121968
Long Hill119821972
Mid Haddam120191973
Southington120231974
New Hartford119871972
Woodstock 2120232017
Warren 2120232015
Granby120221988

Black-billed Cuckoo Population Trend in Other States

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

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