The "Blusher" bird
African Harrier-hawk, formerly Gymnogene – Polyboroides typus (Afrikaans: Kaalwangvalk)
The name Gymnogene (from the Latin “bare-chinned”) for this harrier-hawk was peculiar to the African variety, but has now been changed to bring it in line with international naming conventions. It is a real oddity amongst birds of prey, unlike any other in this group.
The colour is mainly a dark grey, with round black spots on the scapulars and smaller ones on the upper wings. It has fine barring of black and white on the chest. The tail is black with a broad white stripe across the middle and a small white tip. The facial skin is bare, and the legs are also bare, and the colour normally yellow.
They occur all over South Africa, except in the very arid areas: distribution maps show an arch stretching from the south-western Cape inland from the east coast, through KwaZulu-Natal, northern Free State and northern provinces to the Okavango Delta in Botswana, with scattered sightings around Etosha in Namibia and in the Trans-Kalahari Park. They feed mainly on young birds taken from nests, rodents, snakes, bats, birds’ eggs, fish and frogs. They nest in tall trees or on cliffs, the nest being a large platform of sticks built by the birds themselves.
The most unusual feature of the Gymnogene is the knee joint, which allows the leg to bend in all directions, unlike all other birds of prey, whose lower legs can move in one direction only. This flexible joint makes it possible for the Gymnogene to put its foot into a nest-hole of a woodpecker or other bird, then move the claws around inside to grab hold of the chicks. The most popular prey is the Cape Weaver. Once they have found a nesting colony, they hang upside-down on a nest with one foot, wings extended, with the other foot feeling around inside the nest for young chicks to extract.
In January this year we witnessed an interesting performance. Just 60 metres from our front door in Onrus near Hermanus, a small colony of Cape Weavers decided to breed in a tall Saligna gum tree (about 20 metres high), building about twelve nests in all. This caused our neighbour a lot of grief. He had three very special palm trees in his garden, his favourite being a “Ponytail”. The Cape Weaver strips palm fronds off neatly to use as weaving material, and just about denuded the neighbour’s palm tree. He put up at least ten rubber snakes to scare the birds off, but to no avail.
The nests were completed, but four weeks later, when the chicks were about ten days old, a Gymnogene arrived in the gum tree. The weavers were flapping their wings and screeching, but the hawk took no notice. We had a grandstand view of him hanging upside-down on the nests and pulling out the young birds. He emptied three nests and then flew off after eating about six chicks. The next day, at the same time, the hawk came again, this time with his mate. They then proceeded to empty nine nests and on the third day they were back to complete the job.
But then something unusual happened – I would not have believed it if I had not seen it myself. The weavers returned, repaired a few of the nests which were damaged and then bred again in the same nests! Unfortunately we were away after that, and do not know whether the Gymnogenes returned for a second slaughter of the young weavers.
Another interesting story about the Gymnogene is of a nest on a cliff at Montagu. There was one chick in the nest (which is usual for this species). Peter Steyn and I set up a hide and spent three whole days observing the birds when the chick was about 14 days old. The female was on the nest most of the time, to be relieved by the male when he brought prey two or three times a day.
Then a troop of baboons came along the cliffs above the nest, rolling down rocks and making a ruckus. The bird sat still on the nest in an upright position, with the facial skin pale yellow all the time the baboons were near. When the baboons moved off, the bird relaxed and the skin turned pink. Eventually, when all was quiet and the Gymnogene was about to fall asleep, the skin turned deep red!
I have never observed the courtship behaviour of these birds, but according to the literature the bird’s face also flushes red during mating.
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