Vocal, Furtive Parasites… Australian Cuckoos

By Keith Hutton on November 24, 2015 in Other

There are over 130 species of cuckoos worldwide and about a third lay their eggs in nests of other birds, which then incubate the eggs and rear the young cuckoos. This parasitic behaviour has been known since ancient times, and documented for over 2000 years by early Indian and Roman writers. It was probably first described for Common Cuckoos, which also have the distinction of being the species responsible for the family name. This relates to their familiar, monotonous, far carrying ‘kuk-kooh’ call, which is traditionally associated with spring throughout their breeding range across Europe and Asia. In Australia, 12 species of cuckoos are regularly recorded; 11 of these are brood parasites and in the Eastern Suburbs seven of them can be heard calling regularly in season.

Typical cuckoos range in size from the huge and impressive Channel-billed Cuckoos, which are much bigger than currawongs, down to the smaller bronze cuckoos, which are hardly bigger than sparrows. They are slender, streamlined birds with long wings and tails, and down-curved bills. You will have no problem hearing them when they are around because their calls are generally clear, persistent, or both, however none of them remotely resemble the ‘kuk-kooh’ call of their northern cousin. Australian cuckoos are more often heard than seen, but they are not too difficult to locate in local parks and gardens, or residual bushland in the settled suburbs, despite their furtive nature.

The two biggest and loudest cuckoos in Australia are migrants that visit in summer to breed. Adult Channel-billed Cuckoos eat mainly fruits from native trees and other sources, vegetable matter, insects, and occasionally eggs and young birds; Eastern Koels eat fruit too, especially figs. The smaller local cuckoos eat insects and their larvae, with a strong preference for hairy caterpillars.

Cuckoos are distributed throughout the world in a wide variety of habitats. Many, especially temperate zone species, are long distance migrants, and in Australia one or more species occur in all states and territories. Fruit eating cuckoos prefer rainforest, woodland and fruiting trees on farmland, parks and streets. The insect eating species are found in a wide range of open forest, woodland, heath land, mangroves, scrublands, pastoral country, golf courses, roadsides and gardens. Whether or not the location is wet or dry, or the vegetation open or dense, there will be at least one cuckoo species there for part of the year.

Migrating cuckoos are occasionally killed by striking lighthouses or by flying into reflecting windows, and young birds may be killed by cars or by cats. Despite these negative impacts, both Channel-billed Cuckoos and Eastern Koels have increased in numbers and are thriving in the Sydney region where their populations appear to be secure. Channel-billed Cuckoos are probably commoner in the Eastern Suburbs now because of an increase in numbers of Pied Currawongs, which are their primary hosts. Furthermore, currawongs, and both fruit eating cuckoos, have possibly benefitted from improved food supply following increased planting of exotic berry trees throughout suburban areas.