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Intraspecific nest parasitism of cavity-nesting wood ducks: costs and benefits to hosts and parasites

In some species, females lay eggs in the nests of other females of their own species, and thereby, parasitize parental care from the female attending the nest. We examined costs and benefits of this parasitism to hosts and parasites in wood ducks. Hosts laid fewer eggs when parasitized and hatching success declined as the number of eggs increased, but most unhatched eggs were laid by parasites. Incubation was longer for large clutches, but associated costs were low compared to those for clutch replacement. For parasites, lower hatching success was more than offset by avoiding incubation. For those females that both incubated a nest and parasitized, allocation of eggs among nests was influenced by costs of incubating additional eggs, hatching success, and any safety against predators for eggs in large nests. These findings help explain the high prevalence of this behavior in birds with limited parental care.

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