While driving through the savanna landscape of Southern Cross Estate (about 15km due south of Nelspruit on the edge of the Barberton Valley) I noticed a large eagle perched close to the top of a massive skeletal gum tree. The tree was at least 30 metres tall and had probably been ringbarked and killed as part of the estate policy to remove alien vegetation. Raptors just love to perch in big bare trees, however, and when I got my binoculars onto it, I could see that it was an African Crowned Eagle. Huge and awesome, it is regarded as the continent’s most powerful eagle – feeding mostly on monkeys, hyrax and duikers.
Although some way off, I was quite certain it was female – always considerably larger than the male. I came to this conclusion because I was able to compare it with a small group of birds that were mobbing it in an attempt to drive it away. The birds in question were White-crested Helmet-Shrikes and it was quite astonishing to witness their aerial prowess and bravery in taking on such an adversary. These small birds go about in family groups (they are cooperative breeders) and typically forage for insects low-down in trees, less often in the canopy – I’ve never before seen them in such an exposed position. They were obviously so concerned about the eagle that they attacked it at the top of this giant Eucalyptus.
The helmet-shrikes took turns to dive-bomb the eagle and I couldn’t help thinking how strangely appropriate their name had become (in reality, the ‘helmet’ is nothing more than a short, forward-pointing crest of feathers!). Each bird would fly up from a perch, get a few metres above the eagle, then fold-its wings to stoop like a falcon and actually clip the top of the eagle’s head! Several times I saw this happen, but the eagle did not appear to be overly concerned by the repeated strikes and held its position.
It is quite normal for small birds to mob goshawks, owls and eagles – in a bid to drive them out of their own territories – but such bold anti-predator behaviour is something that I have previously only ever seen Fork-tailed Drongos engage in.
Southern Cross Estate, Nelspruit, South Africa. November 2013