A bird in a very tall tree
Palmnut Vulture – Gypohierax angolensis (Afrikaans: Witaasvoël)
The Palmnut Vulture, as it is known today, used to be called the Vulturine Fish Eagle; this I feel is the more suitable name for this interesting bird, as it does not have the scavenging habits of the typical vulture. The bird is a bit small for either a vulture or a fish eagle (it weighs only about two kilograms). Its bill is long and curved like an eagle’s, the legs are long and bare with very strong toes with decurved talons like an eagle's, but the bare skin around the face and eyes gives it a vulturine appearance. In flight it definitely resembles an eagle, but on the other hand it has a barking, vulture-like call.
To learn more about the private life of the Palmnut Vulture, Hugh Chittenden from Eshowe and I in 1994 decided to build a hide at the nest of a pair of these birds at Mtunzini in northern KwaZulu-Natal. At that stage no photographs of live Palmnut Vultures existed – the single record in the British Museum had been obtained by shooting a bird on its nest.
Palmnut Vultures invariably nest in the crown of a Raffia (or Kosi) Palm, Raphia australis, which was first introduced into the Mtunzini area from Mozambique at the start of the twentieth century, and in the 1960s further distributed in the area by conservationist Ian Garland. The Raffia Palm is a very tall tree with leaf fronds of up to 18 metres long – the longest leaves of any tree in the world. When this palm was established at Mtunzini, the Palmnut Vulture, a tropical bird from Angola and Mozambique, soon followed.
The Raffia Palm bears only one crop of fruit in its lifetime of about 20 years, but then it bears all its nuts in one great cluster of up to 6000 nuts with a mass of 1000 kilograms. When the fruit is mature the tree dies, but the single crop gives the birds a plentiful supply of very rich and nutritious fruit. The nuts are about the size of a big hen’s egg, covered with large scales. The birds expertly pull out a fruit, strip off the scales with their specially adapted beaks, and then scrape off the two-millimetre layer of yellow flesh with a sideways movement. After all that effort the bird only gets about one tablespoonful of food, but luckily there is a lot of it.
Hugh Chittenden was the mastermind of our whole vulture-watching operation and also handled the construction of the pylon hide in his workshop. It consisted of borehole linings 14 centimetres in diameter welded together to form a singe column 25 metres long, with steel slats welded onto the side of this core to form a ladder.
The hide was transported down to the nest site at Mtunzini and erected with the friendly cooperation of the municipality. Three sets of stay wires were attached to Umdoni trees (Syzygium cordatum), as one could expect very high winds in the summer months, often of gale force. Once completed, the hide was one of the tallest structures at Mtunzini! We put up a big notice saying that this was for the scientific study of the Vulturine Fish Eagle (at the time) and anybody interested in joining the research would be welcome. We did not get a single application. The only people who were prepared to risk their lives along with me were Hugh Chittenden, my wife Ella and son Johan, and fellow-birder Peter Steyn, who especially came all the way from Cape Town.
The Palmnut Vulture makes a huge stick nest lined with coarse grass and after all the trouble of building it, lays only one egg. Incubation is done by both adults, on a more or less equal basis. After an incubating period of 50 days, a dark brown chick emerges. The adults are good providers. About 20 percent of the food they bring in is palm nuts; the rest is crabs, frogs, the large local snails, birds, carrion, large insects, rodents and fish. The chick fledges after about 60 days and then, after the second day, it goes onto the next palm where the fruits are ready and manages to strip the scales off nuts, then scrapes off the flesh itself. It seems this is the only bird of prey that can fend for itself so soon after fledging. However, in spite of this, the adults go on feeding the chick until the next breeding season.
After rains, the puddles next to the road become full of frogs and the Palmnut Vulture then collects up to 20 or 30 frogs at a time, and stores them in a tree “pantry”.
A few records exist of Palmnut Vultures in South Africa outside their breeding area, but they all seem to have been sub-adult birds on their grand tour, like most big eagles undertake before they eventually settle down. In 2005 a Palmnut Vulture was seen for quite a while at Langebaan on the West Coast but then, believe it or not, it was shot by a farmer!
The Raffia Palm will grow outside its natural habitat (there are a few at Kirstenbosch), so next time you go to the nursery to buy a palm tree for your garden, make sure it’s a Raffia Palm. In twenty years’ time you may have a Palmnut Vulture nesting on your doorstep!
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