AROUND THE CLOCK
Australia’s cuckoos range from the world’s smallest to the largest.
CUCKOOS
ARE typically secretive birds, hiding in dense foliage or emitting soft trilling calls from obscured perches. Most are heard well before they are seen, if seen at all.
They are famed for their ‘brood parasitism’ reproductive strategy, laying eggs in the nests of other bird species and leaving unwitting parents to raise alien chicks at the expense of their own. Despite this reputation, about two-thirds of the world’s cuckoo species do build a nest and raise their own young. And yet, the only Australian species to do so is the pheasant coucal.
Australia has 12 species of resident and migratory cuckoos. They range in size from the diminutive little bronzecuckoo, which at just 15cm long is the smallest of the world’s cuckoos, to the hulking 66cm-long channel-billed cuckoo, the world’s largest. Another five species have been recorded here as vagrants.
Although Australia doesn’t have any species that are endemic (found only here), a number of subspecies are, and several more subspecies breed nowhere else.
One regular migrant that’s almost always heard well before it’s seen is the eastern koel, which travels from SouthEast Asia to Australia’s north and east in spring and returns northwards in early autumn. Some individuals also remain in northern Australia year-round.
The eastern koel travels as far south as Victoria and west to the Western Australia-Northern Territory border, and its arrival, for some people, heralds
the beginning of restless nights. The eastern koel is not a true nocturnal species, but it has a rather annoying habit of emitting its familiar “ko-el” call through the night.
Not only is the eastern koel’s call loud, it is also produced repeatedly in quick succession and rising in pitch, as if to ensure that even the soundest sleeper is awakened from their slumber.
The call is also made during the day, perhaps so as not to discriminate against night-shift workers!
The male eastern koel is dark blueblack with a striking red eye, while the female and young birds are more cryptically coloured in blacks, browns and buffs, with a dark eye.
The female eastern koel typically lays a single egg in multiple nests, targeting larger honeyeaters, including the red wattlebird and different species of friarbird, as well as figbirds and the magpie-lark. The egg is disguised to look like those of the host species and the female eats one of the other eggs to distract from her crime.
Cuckoo eggs hatch quickly and the hatchling forces other eggs or hatchlings out of the nest or outcompetes the other nestlings for food. Not all host birds are duped though and, if detected, the alien egg will be ejected.
Despite the overall success of the parasitic reproductive strategy for the koel, populations of host species are not significantly affected.