There are relatively few nest records for Mangrove Cuckoo, but the clutch size is probably 2-3, less commonly 4 (Bond 1941, Clark 1905, Davie 1889, Gleffe et al. 2006).
The breeding season appears quite variable, perhaps reflecting the diversity of environments inhabited by this species. Nesting generally seems to peak in May – July throughout the range of the species (Bond 1941, Sutton et al. 1950, Grant and McT. Cowan 1964, Holland and Williams 1978) although evidence suggests that birds may breed at virtually any time of the year if conditions are suitable. For example, Tye and Tye (1991) observed courtship feeding and copulation in late February on San Andres and Providencia, and Davie (1889) reported the breeding season in Jamaica as running from March – July. On the other hand, Bowdish (1902) collected a gravid female on Puerto Rico in September. Museum specimens also suggest an extended breeding season; individuals in hatch-year plumage have been collected in every month of the year (J. Lloyd, unpublished data). Populations in strongly seasonal environments, such as many of the islands of the West Indies, may breed primarily around the transition from the dry season to the wet season, whereas individuals in less seasonal environments may breed year-round.