Colours of Wildlife: Great Spotted Cuckoo

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Great Spotted Cuckoo

Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

Great Spotted Cuckoo by Willem

We're back to the contemporary world of wildlife again. This is a Great Spotted Cuckoo, Clamator glandarius. It is large for a cuckoo, at about 35-40 cm/14"-16" in overall length. The scientific name means roughly 'shouter of the acorns'. The species occurs in southern Europe, the mid-East, western Asia (Turkey to Iran) North Africa and much of sub-Saharan Africa. It breeds both in the north and in the south of its range, and is found in the central parts (tropical Africa) throughout the year. South African breeding birds may come from Europe, Asia or from further north in Africa. In Eurasia this species likes fairly open woodland or groves of oak, pine or olive trees, while in Africa it occurs in dry, thorny woodland, bushland and savannah. It is a true, brood-parasitic cuckoo.

Parasitizing the Pies

The great spotted cuckoo in Africa as well as in Eurasia parasitizes members of the crow family, as well as some starlings. In Spain it often parasitizes the two species of magpie that occur there, the Black-billed Magpie Pica pica and also the Azure-winged Magpie Cyanopica cyanea. The cuckoos with their long tails are similar in size and shape to the magpies, and young birds are often seen hanging out with their magpie families before finally embracing their cuckoo-hood and heading off on their own.

It is understandable that these cuckoos should parasitize the magpies and starlings, which are close to themselves in size, but rather strange in that they also, both in Europe and Africa, parasitize crows that are much larger than themselves. Most cuckoos choose hosts smaller than themselves. The typical way cuckoos parasitize their hosts starts with an attempt by the male to do an impression of a small hawk – this he does with his hawk-like silhouette, coloration and style of flight. The target hosts will then try to drive off this potential predator. While the host couple is distracted by the male, the female cuckoo slips into their nest. She has a long, extensible cloaca so that she can rapidly lay an egg or two in the host's nest. She may, if she has time, throw an egg or two of the host's own eggs out of the nest. Having finished the job, she'll rapidly vacate the premises and her mate will join her. The hosts return to the nest, where they may recognize the new cuckoo egg, in which case they'll destroy it or throw it out, or even entirely abandon their clutch and start a new nest. But in enough cases, they'll suspect nothing and incubate the cuckoo egg along with their own. Typically the cuckoo egg will hatch faster than the hosts' own eggs (aided by the fact that the cuckoo female can keep an egg in her body for a day during which time the embryo already starts to develop). The baby cuckoo will also be larger than their own chicks, and to boot may call for food louder and more frequently, prompting them to give it more food. The cuckoo chick may also throw the eggs of the host that haven't hatched yet out of the nest, or do the same to any host chicks that have hatched. But if any of the hosts' own chicks do manage to hatch and remain in the nest, they're so dominated by the cuckoo chick that they may starve. The hosts will happily raise the cuckoo chick, which in many species may end up far larger than its foster parents. Indeed in Europe the cuckoo in myth is supposed to end by swallowing them as well but this isn't true!

That's the typical brood-parasitic-cuckoo way, and the great spotted cuckoo doesn't differ much from that, except as I said in often choosing hosts bigger rather than smaller than itself. In South Africa, the typical host is the Pied Crow, which is very much larger than the adult cuckoo. The eggs of the cuckoo look very much like those of the crow, but are smaller. Unlike other cuckoos, the female great spotted cuckoo does not remove eggs from the host nest, but may damage them by dropping her own eggs onto them. The advantage the cuckoo has is that its eggs hatch more rapidly than the crow eggs, and the young cuckoo chick has head start in growth and feeding. The chicks have brighter, more conspicuous gapes, and more horny spurs on their palates than the crow chicks do. It is thought that both the gapes and the spurs are visual stimuli for the crows to feed the chicks. The cuckoo chicks also have calls that sound like those of the young crows and magpies. They have displays and defenses against predators: they will open their bills wide, displaying the bright gape, and lunge at potential predators; they also squirt out foul-smelling, watery excreta at them. All of this gives cuckoo chicks a considerable survival advantage. But sometimes some of the host chicks do survive and are raised along with the cuckoo. This happens more often with the larger crows than with the magpies.

While usually a female cuckoo lays only a single egg per nest, sometimes she may 'dump' numerous eggs in a nest. The record is thirteen cuckoo eggs in a single crow's nest, but these may have been from more than one cuckoo female. While crows are the main hosts, starlings of several species are also sometimes chosen. These are smaller than the cuckoos and thus more 'typical' hosts compared to other cuckoos.

It is important to note that the cuckoos dare not be too successful: if they parasitize all the nests of their hosts, then the hosts will rear no chicks of their own, meaning that eventually there would be no more hosts for the cuckoos. There is thus a balance that nature imposes. In practice, the great spotted cuckoo is much rarer than its hosts, and can therefore not have that much of an impact on their numbers. Brood parasitism means that the adult cuckoos save on child-rearing costs, but must take a lot of chances because of the risk of hosts that are not deceived. In practice, a female great spotted cuckoo may lay as many as twenty-five eggs, laid at intervals of two days or more, in other birds' nests each season. Obviously of that number only one or two may be successfully reared each season, thus keeping the number of cuckoos fairly stable.

In their life apart from breeding, great cuckoos are typical. They forage mostly in trees but sometimes on the ground. They are insect eaters, and specialize on hairy caterpillars. These are the young of butterflies and moths, and the long, stinging hairs that cover them are for defense. While most birds consequently avoid these caterpillars, the cuckoos appear to tolerate them, using their long bills to rub off the hairs and then swallowing them whole. They also eat adult moths, grasshoppers, termites and small lizards.

Like most cuckoos, the great spotted cuckoo has a distinctive call. In the breeding season, the male will sit on top of a tree for almost the whole day long, uttering a loud, harsh, 'gah-gah-gah-gak-gak-gak-ko-ko-ko' call that falls in pitch and increases in tempo as it goes on. By this means the male stakes its claim to a territory and attracts females. Once a mate has accepted him, he will present her with food, and they will preen each other, to strengthen their bond. It is possible that this species might be polygamous.

The great spotted cuckoo is a very widespread species, though nowhere common. It is not considered threatened at present.

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