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Brood parasitism by the enigmatic and rare Pavonine Cuckoo in Amazonian Peru

Sánchez-Martínez, Manuel A., David, Santiago, Londoño, Gustavo A., Robinson, Scott K.
The Auk 2017 v.134 no.2 pp. 330-339
Cuculidae, birds, brood parasitism, color, eggs, hosts, nestlings, nests, parasites, plumage, reproductive success, Amazonia, Peru
Brood parasitism is an uncommon and understudied strategy in Amazonian bird communities, within which only 5 species are known to be brood parasites. We present data on the brood-parasitic behavior of the Pavonine Cuckoo (Dromococcyx pavoninus) in 3 host species of small-bodied flycatchers in the Peruvian Amazon that construct hanging globular nests with side entrances. During the 7 yr of the study, we encountered 74 nests of these 3 hosts, but parasitism occurred only in 9 nests (12.2%) in 2 yr. Only 1 Pavonine Cuckoo egg was deposited in each host nest (n = 7), and eggs were markedly dissimilar in size and coloration between hosts and parasite. Incubation investment per day was slightly higher (4%) for 1 parasitized nest than for nonparasitized nests. Overall, 33% of parasitic eggs (n = 6) hatched; cuckoo nestlings apparently removed host eggs and killed host nestlings. The nestling period lasted 24 days, and the growth-rate constant based on nestling mass (k = 0.23) was slower for parasite nestlings than for their hosts (k = 0.27 and 0.31). Food provisioning rates were greater in 1 parasitized nest (2.1 ± 0.7 feedings hr⁻¹ nestling⁻¹) than in nonparasitized nests (1.1 ± 0.4). Nestling cuckoos may further mimic the plumage of their host nestlings. Our results suggest that Pavonine Cuckoos negatively affect their hosts' breeding success and are engaged in a coevolutionary arms race with hosts that have defenses against parasitism.