24 June 2014 by Andrea Weiss

The eagle has hatched

Watch how a pair of Verreaux’s eagles (also known as black eagles) raise their chick in real time in a Johannesburg botanical garden.

The Verreaux's eagle is one of southern Africa's iconic birds of prey. Image courtesy of Derek Keats

First there were two ... and then there was one.

In a recent blog we talked about Eagle Cam, a remote camera set up on a 50m-high cliff in the Walter Sisulu National Botanical Garden in Roodepoort, Johannesburg, where a pair of Verreaux's eagles (formerly known as black eagles) is currently breeding. 

Emoyeni, the female eagle, patiently sitting on her nest Emoyeni, the female eagle, patiently sitting on her nest

These two eagles are much-loved by garden visitors. 

Each year, there is much excitement when the breeding season begins, usually with the laying of a clutch of two eggs in May. For around 45 days, the female (known as Emoyeni) sits on the eggs until they hatch out.

About a week ago, the eggs hatched, setting in motion the next part of the drama, the Cain and Abel struggle, also known as 'Cainism' or 'siblicide'. This is a reference to the biblical story of Adam's sons Cain and Abel, whereby Cain murdered his younger brother out of jealousy. 

In the case of nesting eagles, there's a more pragmatic biological reason for the stronger of the two chicks to kill, or squeeze out, its nest mate: it's nature's way of ensuring that there's at least one healthy youngster at the end of the breeding season. 

The remaining chick preens itself while waiting for a parent to return The remaining chick preens itself while waiting for a parent to return

Verreaux's eagles are one of the species that practise what is called 'obligate siblicide', whereby the last chick to hatch always succumbs to a combination of hunger and bullying by the elder chick. The reason why the eagles lay two eggs is a form of insurance, as if one egg fails there's still another to hatch.

But once hatched, the parents are not able to provide enough food for two chicks (a young eagle can eat several times its weight per day) and so only the strongest bird survives.

Although I did not witness the demise of the weaker chick, it was already evident last week that the mother was favouring the stronger of the two, feeding tasty little morsels to it persistently, with the weaker chick not getting a look-in.

The next time I checked, there appeared to be only one chick left, and it had doubled in size.

Mom and chick reunited Mom and chick reunited

With this gory bit of business out of the way, however, it's now possible to watch how these two eagles raise their new baby, a process that will unfold over the next three months as the chick grows large enough to learn to fly on its own. 

Even once it's flying, it will remain dependent on its parents for several months before heading off to find a new territory of its own and, of course, a mate to start the whole process all over again.

A Verreaux's eagle in flight. Image courtesy of <a href= A Verreaux's eagle in flight. Image courtesy of Derek Keats

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