Crowned Eagle Research in KwaZulu-Natal: ... to build a nest

This is the story of one eagle pair and their struggle to build a nest. With a little help and intervention they are off to a fine start for this year.

The recent history follows:
It begins in 2010 – when a pair of Crowned eagles arrived to build a nest on the lower end of the Victoria Country Club Estate. The nest was being constructed about midway up a tall gum tree. A large lateral snag leaned out providing a crux for the foundation. The egg hatched on the 10th of November 2010, and the residents of VCCE followed intently the development of this eaglet. People were watching every day, and Ron was there the moment this eagle, christened “Jeffrey”, took his first flight on the 13 of February 2011.

As typical of these young eagles, Jeffrey leeched off his parents for the rest of the year, and as the summer of 2011 moved in – wind and rain took its toll on the nest site. The whole construction fell away. Nothing was left. If these eagles, like others around, were going to breed every second year, they would need to prepare a new nest from scratch.

I first arrived on the scene in early May. First contact was with Ron Perks, he was delighted to pass on all the details of Jeffreys growth to independence. With Ron and Kelson Camp, we went down to the gum stand to show me where the nest used to be. I mentioned that the pair could well return to breed again this season – but where. In June they were being seen around more and more often.

Despite his proclaiming me the fundi in eagle matters, Ron’s interpretation of eagle behavior seems to be spot on. And during the next few months I was easily able to deduce what these birds where up to from his descriptions. Despite the reluctance of biologists to anthropomorphize animal behavior, it doesn’t seem to do any harm – afterall, in more recent years the community has been served several helpings of humble pie when we discover, for example, chimpanzees have culture, dolphins have language, and elephants grieve for lost family members. The eagles pair up and have a strong bond with each other, personalities shine through and it seems each pair has their unique relationship quirks.

A quote from Ron’s notes to the VCCE residents goes as such

18 June 2012
Bill Farrell phoned me from their stand at VCCE, to say the eagles were in last year’s nest tree and the male was flying in sticks to the top of the tree. He was doing his best to start a base so as to start building a nest. However it was an impossible place to make a nest as every branch or stick he flew in would fall out of the tree. He tried for a whole week to get the nest started where she wanted it and she just sat and watched. It made me think that with all the effort he was putting into building this nest, she must be a good catch!
27 June 2012
I phoned crowned eagle expert Shane Mcpherson [sic], who had visited the nesting site, and told him that the male was failing in his bid to win the female’s attention as he could not start the nest in the spot she wanted…

The location for the 2010 nest was no longer an option, the small snag was all that remained of their main bracing branch. The tree rises and rises 40 meters up to a three-way fork just shy of the top of the crown. This is where they decided to try and rebuild. The fork was comprised of stems only the girth of my thigh, and whenever the wind picked up slightly, the top third of the tree would tilt and sway. It was totally inadequate. This was no place to build a nest. Oddly, despite there being many other possibly nesting sites in nearby gum trees, the eagle just HAD to have their nest in THIS tree. So they tried and they tried.

For three weeks the male would fly to a nearby quinine tree, consider his options before selecting a branch. Jumping onto it and tussling with the tree, sometimes comically, he would eventually succeed in breaking large branches and swooping across to the nest. Every time the wind blew the gum tree would tilt and shake. Many hopeful VCCE residents would watch to see each branch tumble to the ground. The female too would be accompanying the male much of the time. She was often very nearby – watching her mate toil away, and apparently with a critical eye. Most of the time she did not assist. Homemaking is the males charge apparently.

I had head of a few instances where artificial nest platforms have been successful. Locally, Ben Hoffman of Raptor Rescue has on several occasions constructed a platform to replace a fallen nest in the midst of a breeding season. Also, I had discussed some months prior with Garth Batchelor of the Crowned Eagle Working Group up in Mpumalanga about their development of a platform. It sounded very similar to the situation we were facing here. So it was worth trying.

After a treacherous track cutting effort through a thicket of carnivorous Mauritian Thorn, Kelson Camp and his team made it to the base of the tree – a request by me so that I could access and climb. I decided that we would try and put in a nice set of bracing beams adjacent to where the old nest used to be – to lure them down to a more accessible, as well as more solid and permanent, nest location.

Though I was chuffed at my handiwork, it at first did not look promising. We left the eagles to their ways over the weekend – all the while the male continued to ignore my design and keep flying Quinine branches up to the top fork. Each falling away in turn. So rather than leave it to the males dogged stubborn determination I took a chance at attempting to persuade the female to change her focus (and hopefully in turn the males). I took the role of the male eagle for an hour one evening – and left a tempting fresh carcass on the platform, thereby mimicking a prey delivery that a male might do to court his girl.

The female was seen on the platform the next morning – and for many hours sat and relished her prize – at one point the male even snuck under her nose to steal a small morsel and flew to a nearby perch to finish it. YES! From that point on we were on the right track. Nest building could begin in earnest. I visiting a week later and James Walker relayed some weekend observations: on a Saturday, from 7am to midday, James counted 33 branches flown in and added to the construction.

Weeks later with several other nests around Durban well into incubation, the nest was being more beautifully built. An uncountable number of matings were witnessed, they starting mock copulations even as early as June, and so suspense was growing and the possibility that this pair wouldn’t get down to business this year was starting to creep into my thoughts. On the 18th of August I stopped in on a whim to check things out. Just the previous evening Ron had seen the female on the edge of the nest – he mentioned that she was standing there looking very uncomfortable “her vent feathers were fluffed out – like she was wearing an oversized nappy”. I thought it was a perfect description for an eggy bird!

We watched for an hour as the female sat low in the nest, and at intervals got up, strolled around the nest, fussed, looking intently into the nest bowl, and moving back into the bowl and wiggling her brood patch back over the hidden egg. Of note during this time – I watched in amazement for a few minutes as she stood at the edge of the nest, plucking hair of some animals hide and flicking it haphazardly into her nest bowl – this egg needs plenty of warm insulation.