Simon Thomsett

Category: Crowned Eagles | Date: May 06 2008 | By: simonthomsett

The following is an expanded diary on the release of 3 Crowned Eagles and it summaries those opportunities and problems we experienced. The Crowned Eagle is undisputedly Africa’s most powerful eagle. There is a specimen in the Nairobi National Museums with a hind talon that is 4 inches (10 cm) long (although most are 3.5inches), and all are pin sharp. The tarsus and muscles that drive this talon are immense and finely designed passing through an outsized proximal condyl that is tunnel shaped with a twisted a twisted curve for maximum power and grip. That twist can take enormous loads, like the front end torsion rod of a car, cushioning immense shock by absorbing a rotational movement within the tarsus. A large human can jump up and down on that bone standing upright and all it will do is twist a few degrees. The rear talon has the potential to penetrate the chest and heart of animals as big as us. Ten centimetres driven at lighting speed to the hilt like a stiletto dagger in a man’s chest or down the spine will cause fatal injury, no question. The muscles that power those talons are as large as the muscles that power the bone crushing skull of the Spotted Hyena. The result is a bird that carries the largest killing equipment on the African continent. Jaws on wings.
Very rarely they do kill animals up to 60 to 100lbs, although their staple prey is around 5 to 35lbs. Just why they have such enormous potential to kill very much larger prey than their normal fare is an interesting question. I am sure that potential to step out of their normal prey base is crucial for survival of a species that is locked into one area within one habitat that has transient arboreal animals and resident land dwelling ungulates. When the monkey troops leave a Crowned Eagle territory the eagle is forced to take larger animals on the ground. Juveniles too, when finally independent of parental care may lack the skills for hunting agile small and intelligent mammals, and find it easier to catch big prey. Adults have a huge advantage in that they are paired with another and can hunt together greatly lessening the odds against smart monkeys. Almost all records of exceptionally large kills made by other eagles are made by juveniles, not adults. Such foolhardiness may be put down to inexperience, but it still ends up achieving the objective…a full stomach.

Photo 2 .Crowned Eagle foot on glove. Note the massive hind talon and short thick toes.

The biology of the species is on a par with the largest carnivores and this in many ways makes it depart from being a mere “bird” or even another raptor. The plumage of the eagle is striking at close range. The adults are cloaked in a mottled patchwork of black, red ochre and white. In the dappled light of the forest it blends in. At only 25 metres this cryptic plumage diffuses as does the coat of a leopards’ into the background. Its short wings and long tail define it as evolving within forests. In the true rainforests of central and West Africa it is the most significant predator taking the largest share of an immense biomass of medium sized mammals that live for the most part in the tree tops. The selective pressure it exerts forced the small arboreal primates to stick together in organised groups and to communicate. To avoid this predation some grew much larger, denying themselves the ability to forage on the most nutritious part of the high canopy. There is little doubt that those that descended to avoid the ogre from above evolved into us. The Crowned Eagle is no ordinary predator.

Photo 3. Crowned Foot and monkey skull, shadows of an earlier time when our ancestors had lobotomies from above!