Birds that lay their eggs in the nests of other (host) birds are called brood parasites. They leave the foster parents to incubate and rear their young. This behaviour is surprisingly common. The parasitic bird is freed from the duties of nest building, egg incubation and rearing young. The energy saved by this behaviour can then be used for egg production. Here, a clutch of 5 Red-gartered Coot eggs (Fulica armillata) is parasitized by one Black-headed Duck egg, (Heteronetta atricapilla). Although a number of different birds practice brood parasitism, two of the best known examples are the New World Cowbirds and the European Cuckoo.
Royal Alberta Museum
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