Australasian Science: Australia's authority on science since 1938

Masters of Disguise

A fairy-wren feeds a hungry Horsfield’s bronze-cuckoo fledgling.

A fairy-wren feeds a hungry Horsfield’s bronze-cuckoo fledgling.

By Naomi Langmore

To avoid rejection by their hosts, Australian bronze-cuckoo chicks are near-perfect visual and vocal mimics that can quickly modify their call to match the species they are parasitising.

Naomi Langmore is an Australian Research Fellow in the Research School of Biology at the Australian National University.

The full text of this article can be purchased from Informit.

For millenia, Australia’s bronze-cuckoos have tricked other birds into rearing their young. The female cuckoo quietly removes a single egg from the nest of the host and replaces it with one of her own, and the unsuspecting host incubates the egg along with her own clutch.

Upon hatching, the cuckoo chick is naked and blind, and no bigger than your thumb nail. Yet despite its helpless appearance, it is a systematic and ruthless killer. Within hours of hatching, the tiny cuckoo sets about pushing the host’s own eggs and chicks out of the nest, one by one. Then, secure in its position as the sole occupant of the nest, it sets up an incessant demand for food and grows at such a rate that within 3 weeks it is double the size of its foster parents (Fig. 1).

This extraordinary behaviour is called brood parasitism. Although cuckoos are the most famous of the brood parasites, this behaviour also occurs in other birds such as ducks and finches, as well as some species of insects and fish.

Australasia is a particular hot-spot for cuckoos – there are more species of parasitic cuckoos here than in the rest of the world put together. Thus cuckoos are a major factor in the life history of many Australasian birds. For example, ten species of cuckoo breed in Australia, and between them they parasitise around 65% of Australia’s songbirds, with 28% being major cuckoo...

The full text of this article can be purchased from Informit.