The Common Koel is a large cuckoo
that arrives in Australia from south-east Asia to breed in spring.
Koels arrive in September or October and depart again in March. Although rarely seen, Koels are well
known to many Australians for their loud, repetitive calls, which
are particularly noticeable early in the morning.
Description: When seen, the male Common Koel is easily identified by its entirely glossy black plumage, tinged with blue and green, and striking red eye. The female has glossed brown upperparts, heavily spotted with white, and a black crown. The underparts are generally buff-cream with numerous fine black bars. Young birds resemble the adult female, but have considerably more buff and a dark eye. The Common Koel is a member of the cuckoo family. Adults are rather shy and they are heard much more than seen. In contrast to the adults, fledglings can be very conspicuous as they beg loudly for food from their foster parents.
Habitat: Common Koels are found in tall forests and are common in suburban areas.
Feeding: Common Koels feed almost entirely in the canopy of trees. Occasionally mixed flocks are formed with other species such as pigeons. Food consists of fruits, especially figs, taken directly from the tree.
Breeding behaviour: Like most other cuckoos, Koels do
not build their own nests or incubate their own eggs.
Instead, females lay their eggs in the nests of other birds.
These 'hosts' incubate the eggs and feed the resulting young
after they hatch. A single egg is laid in the host's nest and once hatched the chick forces the other eggs and hatchlings out of the nest. When the chick leaves the nest it roosts in the outer branches of a tree, cheeping incessantly while the significantly smaller parents desperately search for sufficient food to satisfy the nagging youngster. This is a full-time job, as the young Koel will grow to nearly twice their size. For example Koels weigh around 190 g, compared
with 95 g for the Olive-backed Oriole and 90 g for the
Magpie-lark, two of its common hosts. Other hosts that have
been recorded include the: Black-faced Cuckoo-shrike,
Blue-faced Honeyeater, Figbird, Grey Shrike-thrush, Helmeted
Friarbird, Little Friarbird, Noisy Friarbird, Red
Wattlebird, Silver-crowned Friarbird, Spangled Drongo,
Victoria's Riflebird, White-bellied Cuckoo-shrike and
Yellow-throated Miner. Eventually, it migrates northwards,
usually later than the adults, to return as a breeding bird
the following spring.
Territorial behaviour and calls: Male Koels occupy a home range of perhaps 75 ha (although this is poorly known), in which they advertise their presence by repeated calling, mostly with the 'ko-el' call. They also produce a 'wurroo-wurroo-wurroo' call and there is some evidence that the latter call becomes more common later in the breeding season. Females are attracted to the male's calls and they produce a 'keek-keek-keek-keek' call of their own. Sometimes females will sing in a duet with the male's 'wurroo-wurroo-wurroo' call, resulting in a 'keek-wurroo-keek-wurrooo-keek-wurroo-keek-wurroo-wurroo'! After copulation, the female lays a single egg in the host's nest. The same female lays eggs in the nests of numerous hosts and these may be within the same, or a different, male's home range.
Increasing abundance of Koels: Koels eat fruit as well as insects, and they are particularly common in rainforest habitats, which tend to have a higher proportion of fruiting plants. They also appear to be becoming more common in cities, such as Sydney and Brisbane, perhaps because of the abundance of ornamental plants and weeds that produce berries. However, another factor that probably contributes to their increasing abundance is the proliferation of some of their hosts, particularly the Red Wattlebird.
References: Higgins, P.J. (ed) 1999. Handbook of Australian, New Zealand and Antarctic Birds, Volume 4 (Parrots to Dollarbird). Oxford University Press, Victoria.
Maller, C.J. 2001. Vocal behaviour of the Common Koel, Eudynamys scolopacea, and implications for mating systems. Emu 101: 105-112
Photos: Copyright N.Fifer

grey plumage.