broodparasitic

Brood parasitism is a reproductive strategy in which one species relies on another to raise its young. A brood parasite lays eggs in the nests of host species, leaving the host to incubate the eggs and feed the parasitic chick, often at the expense of the host’s own offspring. The behavior occurs in birds and, less commonly, in other taxa. In birds, it ranges from obligate brood parasitism, where the parasite relies entirely on others to raise its young (examples include the common cuckoo and various cowbirds), to facultative forms, where a species may parasitize others but also raise its own young.

Parasite chicks often hatch first, may mimic host eggs or nestlings to avoid detection, and in some species will evict or outcompete host eggs or young. Hosts respond with defenses such as recognizing and rejecting foreign eggs, abandoning parasitized nests, or otherwise reducing the parasite’s success. This interaction frequently drives coevolutionary dynamics, influencing life histories, behaviors, and population outcomes for both parasite and host.

Intraspecific brood parasitism, a related phenomenon, occurs when individuals lay eggs in nests of their own species, a strategy observed in some waterfowl, shorebirds, and other groups. Brood parasitism can also occur in other animal groups, including certain insects that exploit parental care. Overall, brood parasitism highlights diverse reproductive strategies and the evolutionary arms races that shape ecosystems.