Cuckoos on a mat appear
The name “Cuckoo” is a classic onomatopoeic name or something named after the sound it makes. However, the “Cuckoo” in this case is the sound made by the migratory European bird, which is one of only two members of this family in Europe. In Western Australia we have ten members of the family, ranging in size from the 60cm, Channel-billed Cuckoo to the 16cm Little Bronze-Cuckoo (neither of which are seen in the Great Southern). All species, apart from one, lay their eggs in the nests of other bird species, leaving them to be incubated and their chicks raised by the duped foster parents. None has a call resembling “cuckoo”!
We can reliably see three species in and around Denmark: the Fan-tailed Cuckoo, the Shining Bronze-Cuckoo and Horsfield’s Bronze-Cuckoo. A fourth species, the Pallid Cuckoo, is now less frequently seen than in years past.
The Fan-tailed Cuckoo is the largest of the three and has a slate-blue back, pale rufous breast and barred tail. It’s has a loud trilling call often uttered from an exposed branch. It prefers to lay its eggs in dome-shaped nests near the ground such as thornbills, scrubwrens and fairy-wrens. It is thought that the darkness of the inside these types of nest help to obscure any unfamiliar characteristics of the cuckoo egg.
The other two Bronze-Cuckoos have striking barred underparts and green iridescent backs which gleam when in the sun. The less common Horsfield’s has a broad eye-stripe which differentiates it from the Shining Bronze-Cuckoo. Both species are migrants to the south coast, usually arriving in late winter or early spring. Like the Fan-tailed Cuckoo, they generally select thornbills and fairy-wrens to do their parenting for them.
There is a fascinating “arms race” associated with cuckoos and their hosts. The cuckoo egg has to be similar in size and colour as that of its host and is laid at a more advanced stage of the host bird’s incubation so that the cuckoo chick hatches sooner and can eject the host eggs from the nest. Equally the host is trying to prevent its nest from being parasitised and it has been shown that some unhatched chicks actually call and this is recognised by the parents, which can then reject any egg not making a similar call. It’s all a bit cuckoo!