Construction of the Siyavaya Nest
Aim and Objectives
Black Eagles in southern Africa are vulnerable. Populations in southern Africa have shown a decline in the last 20 years mainly due to habitat loss and a reduction in prey availability. In Namibia they are however classified as near-threatened. In an effort to assist we had an artificial nesting platform built and erected on Meyers’ Farm where we spotted a pair of Verreaux’s eagles.
“The first records of Black Eagles nesting on man-made structures are detailed by Boshoff and Fabricius (1986). These were all in areas where hyraxes were common, but natural features suitable for nesting were absent. This illustrates Newton’s (1979) thesis that a sufficient supply of food will be utilized by a raptor population provided nest sites can be found and suggests furthermore, that nests may be built on unusual sites in order to utilize the food supply. Such opportunist use of man-made structures has also been recorded for other raptors and for vultures (Allan 1988b).” – The Black Eagle a Study by Valerie Gargett
The concept of the ANP for large raptors has been in existence for approx. 35 years and extensively used in many European countries and the Americas to accommodate highly threatened birds of prey such as Osprey (Pandion haliaetus) and the Bald Eagle (Haliaeetus leucocephalus) with great success. In South Africa however, ANP projects are still very much in their fledgling stages: the few ANP’s that have been erected over the years did not appear to have been very successful.
The Meyer’s Farm ANP was designed solely in an attempt to lure the eagles away from the highly dangerous power pylon nesting site and a probable recurring deed by Eskom to remove the nest without hesitation. Imperative thus it was necessary to also divert a possible catastrophe of an eagle colliding with the cables and either being electrocuted or maimed.
Almost a month after the juvenile disappeared, I received a call from Toni Niemand, Siyavaya Highway Construction Joint Venture, who informed me (very casually) that they were going ahead with the ANP that we have so longed for. I recall that I did fall off my office perch! The enormity of such an incredible and generous gesture was immense and all we had to do was to provide the finer details.
A true or booted eagle – eagles with feathered tarsi – falling under the genus Aquila.
Scientific Name: Aquila verreauxii
Height 80-96cm; Wingspan 180-220cm; Weight male 3.7kg, female 4.5kg
On Sunday morning 1 March 2009 and only 5 days after erection, both Verreaux’s eagles landed twice on the platform and spent 22 and 27 minutes respectively on the Siyavaya Artificial Nesting Platform. On the second landing both brought sticks to the nest and the female arranged these. Whilst the female was testing the nest cup, the eagles engaged in pair-bonding with the touching of beaks.
An in-depth internet search yielded numerous sites pertaining to Osprey and Bald Eagle ANP’s; we adapted the best of each to suit our conditions. Ten days later I faxed ‘my vision’ to Niemand who in turn handed it to SHCJV construction manager Peter Schoonbee, who handed it over to company technical director Vic Wilson-Taylor, who then handed it down to structural engineer Kuda Mujaji both of UWP Consulting Engineers. Work on the design then began; the ball was rolling. Sourcing the right material for the 15 meter high mast was difficult; my initial idea was a treated timber pole or a felled eucalyptus tree, but the terrain made moving an 18 meter long timber pole to our recommended site, quite impossible!
The initial time frame for erection of the ANP by 12 December was extended when it was ultimately decided that the mast would be constructed from a steel tube in order to withstand wind load tolerances and a magnitude of other issues that went right over my head and that only structural engineers could calculate. Thirty-five pages of in depth “rocket scientist theories” led to what stands erected today. Three 6.100 meter long 324 mm diameter x 4.5 mm wall thickness steel tubes were delivered to Butch Bouwer director of Vital Steel Projects cc. and overseen by Rui Pina and Chris Garside who commenced with the fabrication of each tube that is flanged and stiffened at both ends to facilitate easier bolt fastening and erection on site. The expanded metal clad 1500 x 1500 x 200 mm basket was fabricated and welded onto one end of a tube, and then all was sprayed with a red oxide primer and delivered to site as three individual sections. SHCJV in the interim excavated the large foundation and with a base of reinforced steel, the first tube was cast into the 2000 x 2000 x 1500 mm deep concrete base; it was left to cure for 12 days. SHCJV, with the assistance of sales representative Conrad Caldwell of Sarens South Africa (Pty) Ltd., appointed a 30 ton rough terrain mobile crane to assist with the erection and hoisting of the two remaining tube sections, one of which had the platform attached.
Bundles of old nesting material were collected from the destroyed pylon site and transported to the new site, where numerous additional bundles of sticks of various lengths and thicknesses were also collected and stockpiled for later use. Philip, Teresa Moore, and I revisited the site to construct the eagles’ nest inclusive of the nest cup with leafy sprays whilst the platform section was still on the ground prior to the 24 February 2009 erection date. It usually takes an eagle pair 4 to 6 weeks to build a new nest from scratch, but we managed it in 2 hours – a fraction of the time. To prevent the nest from self-destructing upon hoisting, the base sticks and leafy cup were tied to the platform with cable ties; once the ANP was in its erect and stabilized position, I was to be lifted to the platform to cut the ties and ‘puff-up’ the manmade nest.
We were on site at 06h15; it was heavily overcast and we were hoping that the rain would hold off until after the mast had been erected. Rain during the night converted the only access to the site into a mud bath. The erection team arrived at 07h00 with their Vital Steel Project 8-ton truck carrying scaffolding and crane basket, were they further churned up what was once deemed a roadway! When the Sarens South Africa mobile crane arrived shortly after 07h00 the road was virtually non-existent, and the dead-weight 50 ton four-wheel drive equipped crane managed to get bogged down. A TLB was called to assist by removing the muddy top layers to find some hard drivable surface beneath. It was amazing to see that little (by comparison to the crane) machine in action as it quickly removed layer after layer of the soft gooey turf. The crane bogged down again and the little TLB hooked it up and in reverse gear managed to tow the mighty crane through 70 meters of turf. The crane arrived at the ANP erection site almost two hours late, and then the real work could begin. The top two flanged sections of the tubes with the platform attached were bolted together on the ground and the scaffolding was already erected to the height of the cast-in base tube. The crane started to hoist the 12 meter long tube skywards slowly and Vital Steel Project riggers were ready to receive it and to bolt this extra-long section to the base tube. Whilst work continued, the curious Verreaux’s Eagle pair flew overhead and settled in a dead tree approximately 150 meters northwest of the ANP where they mated – in full view of about 25 onlookers. The pair remained in the tree for at least an hour as if they too were watching the proceedings with much interest. When the 15 meter mast was securely bolted and stabilized, it then started to drizzle.
Documenting the process
Complete with safety gear and loaned hard hats, Phillip Lennon, producer of Coral Tree Films and I were hoisted in the basket by the Sarens South Africa crane to the platform to snip the cable ties that had held the nest intact during the hoisting operation. The view from the 18 meter high platform was absolutely stunning, looking out over the vast 300 hectare bushveld ridges and grassveld plains of Hans Meyer’s Farm. It seemed an incredibly well-suited site. The platform would be every bit as inaccessible as a natural sheer rock face with a full 360 degree surround view for a lucky Verreaux’s eagle pair One kilometer northeast of the ANP we could see the moving traffic but the noise thereof was hardly audible, which is a far cry from the pylon nest site that is situated only 150 meters from the extremely busy Reading Interchange. Another bonus at the site the absence of obstacles or hazards such as power lines, isolators and high voltage jumper cables protruding from each pylon tower.
The cherry on top for this particular site is that it is situated in a natural bowl area where the eagles can obtain an immediate lift-off on the prevailing thermals, something that was lacking at the pylon site. Finally, within the immediate surrounds of the ANP site there are at least 10 natural Rock Hyrax populations scattered amongst the granite outcrops, which should serve as an ideal ‘take away meal menu’ from the comfort of the eagles on their high nesting perch.
Project sponsors and donors
The Raptor Conservation Project wish to thank Hans Meyer owner of Meyer’s Farm for affording us the opportunity to erect the ANP within the safety of his farm, Toni Niemand, Peter Schoonbee and Colleen Clark of Siyavaya Highway Construction Joint Venture for their generous donation of the aptly renamed “Siyavaya Nest”. Without their vision and execution, this nest would have remained just a dream. We equally thank the development team for their donated time and attention during the design, fabrication and construction process to make this long awaited platform become a reality: UWP Consulting Engineers, Vital Steel Projects cc., and Sarens South Africa (Pty) Ltd.
Swartland, Clarens, 9707
+27 (79) 505-6419