Breeding

Dark-billed Cuckoo breeds during October in Colombia, and during October-December in Argentina (Payne 1997). In the Galápagos, the beginning of breeding season occurs simultaneously with the beginning of the rainy season (Ervin 1989).

Unlike many other members of Cuculidae, Coccyzus cuckoos are not brood parasites. The nest of Dark-billed Cuckoo is a flat platform of sticks built in trees and bushes (Payne 1997, 2005), which somewhat resembles a pigeon nest (Sick 1993).

The clutch size is 2-3 eggs in most of the Dark-billed Cuckoo's range, with the exception of Argentina, where it is 3-4 (and in rare occasions 5) eggs (Payne 1997, 2005).

The eggs are a pale greenish blue color (Belcher and Smooker 1936, Payne 1997, 2005). Egg dimensions have been measured as 30 x 23 mm (Payne 1997) and 28.7 x 21.5 mm (Belcher and Smooker 1936).

Like other species of Coccyzus, Dark-billed Cuckoo has a short incubation period and asynchronous hatching with highly variable chick size (Ervin 1989). Ervin (1989) reports that in the Galapagos, "Chicks grow rapidly and are able to move about in the vegetation before they are capable of flight", and that the young closely resemble those of the Yellow-billed (Coccyzus americanus) and Black-billed (Coccyzus erythropthalmus) cuckoos in appearance and behavior, but that the chicks of Dark-billed did not produce a buzzing sound as reported for chicks of the two other species.