Cuckoos - Noisy Deceivers

Parasitic Cuckoos

Although elusive and seldom seen, cuckoos are among the most vociferous of all birds. Fascinating birds in every way, there is still much to learn about their behaviour. The cuckoo family in Africa includes the true cuckoos, which are brood-parasites, and the coucals which build their own nests and rear their own young.

The parasitic cuckoos have evolved a breeding strategy which does away with parental care, but it is not easy for them to simply deposit an egg and leave the foster parents to do the rest. Crafty strategies need to be devised and employed if the cuckoos are to be successful in conning their selected host into believing that they are raising their own young.

Migrants from tropical Africa

In Southern Africa, all cuckoos are migratory (the Klaas's and Emerald Cuckoos appear to be resident in the warmer east), arriving from Central or Eastern Africa at the start of the rainy season in late September and October. Upon arrival, the males establish territories and advertise their presence to females (and birdwatchers!) by calling incessantly, sometimes even after dark. The repetitive "piet-my-vrou" call of the Red-chested Cuckoo and the "I'm so sad" call of the Black Cuckoo are well know to city and country folk alike, even though they may never have seen the birds. The calling of the male cuckoos continues through November into December, but then tails off, even though the birds usually remain in the region until March or April. Female cuckoos call much less and are incredibly secretive. It is doubtful whether parasitic cuckoos are monogamous, although mating is at least preceded with a choice food morsel (courtship feeding) presented to a female by a male. The Striped and Jacobin Cuckoos are an exception, for they do form pair bonds and actually work together to deceive the host.

Furtive females

While the male cuckoos are calling so earnestly, the females are moving through the habitat in search of nests into which they can deposit an egg of their own. Some cuckoos are host specific; the African Cuckoo will evidently parasitise only the Fork-tailed Drongo. Others are less discriminatory - the Diederik Cuckoo has 24 known host species. Nevertheless, it has been shown that female cuckoos raised by one particular species will invariably select the same host species themselves for they have, in effect, been imprinted. It is no easy business for the female cuckoo to deposit her egg, however, since she must not only find the concealed nest of her chosen species, but must find it at the right time! All birds are aggressive in defence of their nest, and will attack and harass any perceived threat. It is critical that the female cuckoo deposits her egg at the right time - ideally within no more than a few hours, and in-between, those of the host's clutch. Most cuckoos are able to produce eggs which match the coloration of their selected host (how is not known!) and the hatching period is often shorter because the female cuckoo can retain her egg in her oviduct for up to a couple of days before laying. Interestingly, cuckoos actually lay their eggs faster than other birds, and the female always removes one of the host's eggs, so that the invasion has the best chance of working.

So, if the female can find a nest, at the right stage, and find a male to fertilise her (the easy part, since males are so easy to find), be evasive enough to elude detection by the hosts, lay her egg, remove one of the host's, and get away unscathed, the next phase of the cuckoo breeding cycle can begin.

The power of the orphan

If the female cuckoo has got her timing right, the young cuckoo will hatch ahead of the other eggs in the brood. Unlike other hatchlings it is completely naked - devoid of even the finest down feathers. Without further ado, the hatchling will use its flat back (other baby birds have a convex back) to ease the remaining eggs (or smaller nestlings) to the rim of the nest, and over the edge. Now, the competition has been removed and the baby cuckoo will be certain to get each and every food item brought to the nest by the parents. With the exception of the Great Spotted Cuckoo which regularly parasitises crows (but just as often starlings), all parasitic cuckoos are larger birds than their hosts, so the job of feeding the youngster is arduous, to say the least. In some extreme cases (e.g. the tiny Reed Warbler and European Cuckoo) the parents may actually perch on the back of their supposed offspring, when feeding it! Soon enough, the foster parents are working overtime to satisfy the ever-hungry baby, oblivious to the fact that it is not one of their own.

Where to see parasitic cuckoos at CCAfrica properties

Seven or more species of parasitic cuckoo can be seen at all the CCAfrica properties in South Africa, Zimbabwe and Botswana between September and April. October and November are the best months for viewing, since the males are so vociferous. Both Phinda Private Game Reserve in South Africa and Matetsi Game Lodges in Zimbabwe are occupied by all three of the beautiful glossy-green cuckoos (Diederik, Klaas's and Emerald) of the genus Chrysococcyx. In East Africa, the same species are present and vociferous during the wet seasons, and in some cases, there may be both a resident and migratory population.

The known hosts of African cuckoos are as follows:
Red-chested Cuckoo - Cape Robinchat, White-throated Robinchat, Eastern Bearded Scrubrobin, Heuglin's (White-browed) Robinchat, White-browed Scrub Robin
African Cuckoo - Fork-tailed Drongo
European Cuckoo - a non-breeding Palearctic migrant
Black Cuckoo - Southern Boubou, Crimson-breasted Shrike, Tropical Boubou, Swamp Boubou
Great Spotted Cuckoo - Pied Crow, Pied Starling, Red-winged Starling, Burchell's Starling, Greater Blue-eared Starling
Striped Cuckoo - Arrow-marked Babbler (possibly other babblers) Jacobin Cuckoo - Black-eyed Bulbul, Red-eyed Bulbul, Cape Bulbul, Sombre Bulbul, Fiscal Shrike
Barred Long-tailed Cuckoo - hosts unknown but African Broadbill is one suspect
Thick-billed Cuckoo - Red-billed Helmetshrike Emerald Cuckoo - Bleating Warbler, Blue-grey Flycatcher, Starred Robin (almost certainly others, still be determined)
Klaas's Cuckoo - various sunbirds, flycatchers and warblers
Diederik Cuckoo - Cape Sparrow, Cape Weaver, Southern Masked Weaver, Lesser Masked Weaver, Spotted-backed Weaver, Red Bishop and Cape Wagtail (commonest among 24 known hosts)

Further reading

Rowan. M.K. 1983. The Doves, Parrots, Louries and Cuckoos of Southern Africa.
David Philip, Cape Town
Oatley, G & G.Arnott. 1998. Robins of Africa. Acorn Books/Russel Friedman Books,
South Africa

Posted: Birds by CC Africa, Date: 21 November 2006