Brood parasites of the bird world

About 1% of bird species on earth are brood parasites that lay eggs in the nests of other species and outsource their parenting duties. Mike Burgess unpacks the dynamics of this exploitative breeding technique.

- Mike Burgess

In Southern Africa, brood parasites include cuckoos, cuckoo finches, indigobirds, honeyguides and whydahs, and they can be divided into two groups: host-specific and generalists, who target specific or multiple species respectively.

Some of these parasites have developed intricate deceptive capabilities, like egg mimicry, to fool hosts into raising their young.

Hosts, however, do not always take this trickery lying down, and in response have developed ways of exposing deception, by for example identifying and destroying an impostor’s eggs.

This process of parasites fine-tuning deception and pushback from hosts can be interpreted as a neverending co-evolutionary ‘arms race’, with numerous nuances depending on the circumstances.

The advantages of parasitism include increased fecundity, as a parasite can dedicate its energy solely to egg production and leave nest building, incubation and parenting to the host. As for hosts, the costs of parasitism include the reduction of fecundity and therefore their very survival as a species.

BROOD PARASITES AND DECEPTION