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Guardians of the urban raptor

Guardians of the urban raptor

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 newly erected artificial nesting 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 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. In 2009 we managed to give such a nest to a lucky Verreaux’s eagle pair and Phillip Lennon was there to document it all. Take a look at his video!

You can find more detail regarding this project by clicking on the button below. Happy reading! 

Guardians of the urban raptor

History KRS and SNR


Klipriviersberg Ridge System (KRS)

For many years and dating back to the late 1950’s, sightings of predominantly individual and occasionally a pair of Verreaux’s eagles have been reported to skirt the ridges and sporadically hunt on the bountiful Rock hyrax (Procavia capensis) commonly referred to as dassie, littering the entire ridge system and found to occupy medium to large colonies.

During 1997, I followed up on some leads pertaining to a possible nesting site within a large eucalypt tree that was situated on an old homestead that has subsequently been incorporated into the greater Klipriviersberg Nature Reserve, but no evidence thereof could be established. During the same year and over a three-month period, just on weekends, we walked the entire ridge system starting from the eastern ridge end at the R59 (Sybrand van Niekerk freeway) and ending on the outskirts of Eikenhof/Naturena close to the N1 Highway in the west. The bulk of our investigation was spent looking for possible nesting sites within the granite boulder-strewn outcrops and ridges that lay scattered along the length and breadth of the approx. 14km ridge system. Apart from the thousands upon thousands of hyrax colonies found in just about every nook and cranny imaginable, the more modernised sites such as storm water pipes / gullies and culverts, illegal rubble dump sites, municipal water reservoir infilling sites inclusive of private garden refuse heaps are all ideally suited for hyrax friendly infiltration abodes. Despite the lengthy criss-crossing of the ridges, we only located two possible sites of which one was above the suburb of Mondeor and the other on Meyer’s Farm close to the Comaro Road slipway off N12 Southern Bypass on the western boundary of the farm. Both sites had a scattering of sticks on rather small ledges of flat outcrop – to my knowledge, too small to occupy a substantial nest over a longer time period. Among the sticks were some bone fragments and the tell-tale evidence of very old and fragmented hyrax skulls and toothless jaw bones. The possibility exists that eagles may have bred there previously, but it would be difficult to determine the age of these sites, which could only be executed via DNA testing, albeit costly, to determine the age of the bone fragments.        

Suikerbosrand Nature Reserve (SNR)

For as long as I can remember, there was always a Verreaux’s Eagle pair nesting on a rocky cliff on the south-eastern slopes of the Suikerbosrand Nature Reserve (SNR). Many raptorphiles, birders and bird club members alike, mentioned the eagles flying overhead, perching on rocks and in trees, as well as seeing them incubating the eggs and chicks growing to juvenile and fledging stages…by far a highlight should you visit the reserve and see them!

Prey should be well stocked for an eagle pair to take up residence in the vast reserve and having telephonically spoken to Heidelberg municipality staff, folk working at the Heidelberg Rekord newspaper and some estate agents, all were in agreement that they were very proud custodians of “their” Black eagles! Prey such as hyrax are in abundance and not deemed to be in limited supply as during the winter months dozens were seen sunning themselves huddling together on rocky outcrops. Apart from hyrax there is good stock of alternative prey such as rock rabbit, scrub hare, guineafowl and francolin, not to mention the occasional monkey troops flitting by…wary and hurriedly!

So, what happened during 2003 when the eagles vacated their nesting site for no apparent reason? As mentioned, there is abundant prey…no interference reported seen nearby, at or on the nest…yet they just upped and left.

It is quite possible that the pair was harassed on or off the nest by baboons, leopard, humans and or a caracal…the latter possibly stands little chance against a formidable pair of eagles with super sharp talons, but it may have taken their chick or juvenile whilst they weren’t in attendance – similarly occurred at Roodekrans during the double clutch breeding season of 1996, when a caracal killed the three-month-old juvenile and thereafter the carcass was entirely dismembered by jackal. Sometimes eagles may feel threatened by predators and as I have witnessed baboons harassing an eagle pair on a farm outside Bela Bela and similarly at Roodekrans, and the aggressive alarm calls by the eagles were possibly enough of a deterrent to chase off the caracal and baboons. However, eagles stand a slight chance fending off a leopard and even a much lesser chance if humans were to destroy the nest and or steal the eggs or a chick! The eagles will defend their offspring at all costs as was witnessed at Meyers Farm when Brett Gardener tried to get to the chick on the nest. Taking the eggs or a chick can thus never be excluded as humans do these things mainly for collection purposes or to raise a pet. During such occasions it is quite possible that the eagles lost their fight against the odds and once “too harassed” they will vacate such a site and move elsewhere knowing that their trusted nesting site offers no protection.

Background of the Aquila verreauxii  

Background of the Aquila verreauxii  

This is a very large eagle. The adult is pitch black with a white ‘V’ on its back and white on the rump. The female has solid white on the back and rump, while the male has the white of its back and rump separated by black feathering. The bill is black, the cere and feet are yellow. White ‘windows’ in the wings are a prominent feature of this species. The wings are broad, narrowing towards body. The juvenile is a mottled golden dark brown with black blotches. The nape and crown are golden brown. The immature bird begins to develop white on its back and rump well into the second year of its life.

General Characteristics of Eagles

The word “raptor” comes from the Latin raptare, which means ‘to seize’. Raptors therefore have clasping talons and hooked beaks with which to catch and tear their prey. There are a total of 84 raptor species in South Africa of which 12 are owls and 9 vultures. Some scientists argue that vultures are not really raptors, as their talons are not very powerful and they do not seize their prey in true raptor style, instead eating carrion and relying on their powerful beaks to tear meat and crush small bones.

Depending on conditions, adult eagles may live for 20 to 30 years, and in common with most long-lived animals have very slow breeding rates and an extremely high incidence of mortality among young birds. On average, only 30% of young eagles survive their first year, and only half of these eventually reach maturity. This situation is acceptable provided the adult survival rate remains high. If the balance is disturbed by unnatural mortality factors such as poisoning or shooting, the population may exhibit a drastic decline or even become extinct.


The Black Eagle is limited to mountain ranges and rocky outcrops throughout Africa (from south to north), but young birds may wander widely. The distribution of these birds closely correlates with that of the Rock Hyrax, its favourite prey. Territory size is determined by prey availability and topography.


Black Eagles are monogamous. The nest is built on cliff ledges and may be used for many years. Within the pair’s territory a number of nest sites may be selected, but one being favoured. They are territorial, so will not tolerate other Black Eagles nesting or passing through their territory. Courtship consists of spectacular flights where both birds fall and climb for hundreds of metres. They frequently drop a stick, especially the male, and then stoop and roll onto their backs to catch it.

Feeding & Hunting

Rock Hyrax  or dassie make up at least 90% of their preferred prey with the male and female often hunting cooperatively with one bird making it obvious to the prey while the other stoops and veers around rocks to surprise the unsuspecting victim. Black Eagles will also hunt guineafowl, francolin, rock rabbit, scrub hare, mongoose and carrion.

Nest building

The nest is built by both the male and female and consists of a platform of large sticks. The cup is lined with green leaves. Old nests can be 2.5m in diameter. The nest is almost always on a steep, inaccessible cliff, but very rarely also in a tree. Two plain white or blotched eggs are laid from April to July (mid-winter) and are approximately 66.7-86.0 x 52.0-62.0 mm in size. Incubation is about 45 days and chicks take about 2 days to hatch. Ninety-nine percent of the time only one chick survives due to the “Cain and Abel” struggle where the stronger (usually older) sibling kills the weaker. The surviving youngster will fledge at about 13 weeks. Once hatched, the nestling spends 3 months in the nest before being able to fly and post fledging will remain dependant on the adults for an additional 3 months when it will be forced out of the territory by both adult eagles. The young bird goes through various stages in plumage growth and reaches adulthood over a period of 3 to 5 years.

On Meyer’s Farm

On Meyer’s Farm

I just got into my vehicle and drove from Centurion to Meyers Farm to ask Hans a huge favour!

During 2003 whilst working on our Hyrax Operation Project – capturing hyrax and reintroducing them into suitable habitat within the greater home range of the Roodekrans eagles – I received a call from Dr Aldo Berruti, then CEO of BirdLife SA requesting me to investigate a call he had received from a lady residing in Lynmeyer directly opposite the Klipriviersberg Ridge along the N12 Southern Bypass. The reason for his call being that pair of “big black birds” was seen by a lady named Audrey Preddy. The following morning I gave Audrey a call and we made an appointment to visit her on the forth coming Sunday. We set up our telescope within the parking lot of their town house complex and waited and just after 13h00 a pair of “beeeg black birds” aka Verreaux’s eagles skirted the ridge flying from west to east on Meyers Farm (MF) a few relaxed figures of eight and then disappeared out of sight. Asking Audrey to be on the lookout for them, she wrote down what she observed and emailed it to me. The next day I phoned Aldo and broke the news that the “beeeg black birds” were in fact Verreaux’s eagles – I had a feeling that Aldo almost fell off his perch with excitement – he requested that we keep tabs on them and possibly launch a conservation observation group. At the time we could not comply with his request, but we promised him frequent feedback of which he was very appreciative.

It was only during 2007 after the finalization of the hyrax capture/relocation project that we could be spending more time with the eagles. During the same year, we also became affiliated to the Birds of Prey Program of the Endangered Wildlife Trust, which made it possible to monitor and observe the birds in earnest. After all, Audrey also kept us well informed and on a weekly basis sending us emails and keeping us up to date!

Meyers Farm

Unaware of where the eagles were hanging out, unsure if they were breeding, let alone where their nest may be (if at all), we had many questions with very few answers. We ventured onto MF and introduced ourselves to the late Hans Meyer, owner of the farm – what a pleasant man! Having sat down with him, he gave us as much information available to him and although he had not located a possible nest, he did say that the eagles came onto his farm about five years ago (2003) and they had been there ever since. He gave us carte blanche to visit the farm whenever we desired and go wherever we needed to go, an appreciative blessing as many farmers are only too wary of trespassers.

Every Sunday was spent at MF and having recruited the voluntary services of Samantha Meyer (not a relative) and two years later, Phillip Tarboton, we really got to grips with the eagle pair. Both Samantha and Phillip resided in Kensington, which was not too distant from the farm and they could cast a watchful eye over them. It took us two Sundays to find out where their nest was despite the eagles trying their utmost to lead us up the garden path. Although they knew that we were watching them, they even built a mock nest on a simple and easily accessible ledge in an attempt to divert our attention from and interest in them – sneaky!

When we found that they were nesting in the first tier of the nearby 210KV Fordsburg/Eiger power pylon, we let them be and kept our observation distance to at least 600-800m observing mostly via telescope. At no time did we want to intrude and jeopardise their vulnerability mainly because they were breeding in an Eskom pylon! 

 A mere 100m north of the extremely noisy Reading Interchange slipway heading towards South Hills, Steeldale and Tulisa Park, the power line most probably became their nest since 2003 as and based on previous research, there was absolutely no suitable nest anywhere along entire approx. 14km KRS extent obligating them to nest within the dangerous pylon. 

Despite the slowly encroaching development within the neighbouring Meyersdal Eco Estate (MEE), gradually reducing immediate hunting habitat and prey availability, the steady influx of vagrants, who live within the hills opposite the N12 Southern Bypass and the South Hills buffer zone, snare the prevailing resources of wildlife which is also the same prey base of the eagles. Although we estimated that there may be as many as 7000 hyrax within 10 sq. km of the pylon nest. Overall, along the entire ridge system there may be as many as 15000 > that is enough to feed at least thirty pairs of eagles for life should they hunt 350-400 hyrax per pair per annum! 

Whenever one is under the impression that all is well and the eagles are untouchable, strange occurrences stick their necks out in that during the 2008 breeding season, and for some unknown reason, the pylon nest was destroyed in its entirety when the nest was breached forcing an 80-day-old  juvenile to fledge prematurely! We searched everywhere to try and locate the eagle, doing ridge walks with 5 volunteers x 50m apart back and forth all along the South Hills buffer zone and inclusive of the entire MEE ridge system all the way from the R59 to the Comaro Street with no sign at all. Having become quite desperate, we recruited the services of the Green Scorpions who executed private investigations at all the “muti” sites within the greater Johannesburg and thereto, producing zero! Assuming us to the fact that the juvenile was lost forever, we surmised that the eagle may have been stolen by some pet collector. The modus operandi of a pet seeker would probably not demolish the entire nest, but you never know especially considering the life threatening dangers of retrieving a bird from a 210 Kv power line. It was only much later, when we were informed that Eskom were the culprits and when questioned about their involvement, they were quick to deny, but also quickly adding that they may have played a part in it. Open questions that remained un- answered for several weeks thereafter and as mentioned previously, Eskom will not tolerate any structure of whatever within their pylons, this was the only conclusive evidence we were able to build on. As far as we know, Eskom was probably involved, we could not prove it as such, but adding it all up, it certainly made a lot more sense as to why they did it and sadly without our advice and or care for the adult eagles and their offspring!

Our juvenile was still missing and having been unsuccessful locating it, as a last resort, we approached the contractors of the Gauteng Freeway Improvement Project who were having a site meeting just off the slipway, asking them to be on the lookout for a juvenile “black eagle” showing them photos of what it looked like and also what the adults resembled. Undoubtedly, all five men were dumbfounded as they never in their wildest dreams would have thought to see eagles along the highway!? We showed them the destroyed nesting site with all the sticks scattered under the pylon as well as a plethora of hyrax bones and skulls that fell on the ground during the destruction process. We noticed an awkward surprise on their faces as one gent said that he thought the birds were crows – I wanted to give him a clip around the ears! They asked me for my contact number and lo and behold I received a call during the afternoon by Toni Niemand, Contracts Director of Siavaya Highway Construction JV (SHCJV), who wanted to meet us at the site office the following morning at 10h00, to which we agreed.   

Toni was accompanied by Environmental Consultant, Colleen Clark of Group 5 Construction, who asked numerous questions about the breeding behaviour of the eagles and why they were breeding in a pylon and not in a tree? They also asked if their continued blasting would prove negative to the eagles as they were blowing the area to pieces a mere 200-300m from the pylon nest. Long term stress levels would probably have a negative side effect to the pair and hence the reason why we could not locate the juvenile at the time. Toni and Colleen were visibly disturbed by my story and Toni asked me what they (Siavaya) could do to help the eagles? Without hesitation I responded by saying that we actually require an artificial nesting platform. He asked me for a sketch and as I was still smoking at the time, I scribbled a sketch on the reverse side of a Peter Stuyvesant pack of 30’s showing him what we had in mind. Later in the afternoon, I faxed him a proper sketch with a whole bunch of notes on it that included the overall height, basket size and shape plus additional fittings and finishes. He called me at the office, thanked me and said he’d be in touch.

I had not heard from Toni for an entire week and I was getting a tad restless and stressful because if we could pull this off successfully it was going to be BIG and much BIGGER yet for the eagles!

I remember the song that The Beatles sang, called “Eight Days a Week” and it made perfect sense as Toni phoned me on the eighth day to let me know that SHCJV were going ahead and that Group 5 would procure the material, UWP Consulting Engineers would design the mast, Vital Steel Projects would fabricate it all and Sarens SA would supply the 35 ton 6×6 all terrain mobile crane to hoist the entire mast into the sky bolting it all together and all we had to do contribute was to build the nest in the basket provided while that section of the mast was still on the ground! I was so delighted and relieved that I just got into my vehicle and drove from Centurion to MF to ask Hans a huge favour! 

Background of the Aquila verreauxii  

Verreaux’s eagles’ breeding

Egg Laying

Usually, in the “wild” eggs are laid from late April to June with a peak in May and only occasionally in July. In an urban environment, eggs are usually laid at least a month sooner, by about end March to early April. It is not known why urban eagles lay sooner but over many years of observing the Roodekrans, Wonderboom and ANP pairs, this trio lay within weeks of another, occasionally within days.


Two eggs are normally laid and three-egg clutches have been recorded at Roodekrans and Wonderboom with the latter fairly frequently as do some pairs in the South-western Cape.  First eggs are always larger, and in some clutches there is a considerable difference in the sizes. Eggs are laid three to four days apart, usually four, and although first-laid eggs may not be incubated on the day they are laid, but at the ANP, incubation commences immediately. During incubation, the eggs are brooded about 92% of the daylight time, with both male and female doing a share, his normally when he brings prey for the female and she leaves the nest to feed on it. During the incubation period, food is never brought to the nest. The female sits overnight, and the male’s share is during daylight varies from pair to pair and at the ANP, the female always sits overnight with the male roosting in a tree fairly nearby.


An egg takes about two to three days to hatch from the time when the first cracks in the shell appear, but before this the chick can be heard cheeping inside the shell. Eggshells are not removed, breaking into fragments that disappear under the nest lining. When the second egg hatches three to four days later, the first chick has already developed its coordination.

Sibling Aggression

A period of relentless sibling aggression occurs during which the first-hatched chick pecks its sibling until it dies from a combination of its injuries and starvation.  As soon as the second egg hatches and the chick starts to move about, it is attacked by its older sibling, who adopts a trucelent posture with chest forward and downy wing stubs held out. Twisting downward pecks are delivered, mainly to the head and back, stimulated by any movement from the second chick. When it tries to come forward to feed, the first chick will attack it. The female makes no attempt to intervene in any way; the attacks may even continue beneath her breast feathers while she is brooding. Gradually the second chick becomes weaker, loses weight, and no longer has the strength to try to feed and succumbs.

Growth Chick

The newly hatched chick is covered in fine white down; the cere and feet are flesh pink, the eyes black and the bill is horn coloured. During its first four weeks the nestling grows rapidly, acquiring a much thicker coat of white down through which first feathers are just appearing along the hind edge of the wings; the cere and feet are yellow at this age. 

The feeble newly hatched chick may receive its first meal when only three hours old. During its first few days its coordination develops rapidly until at the age of four days it can direct accurate pecks at its sibling. Chicks in exposed or sheltered nests would require different amounts of care. The overall picture is clear, in the first few days a parent is on the nest about 98% of the time, and the chick is brooded a great deal; the male assists in this, but his share is small, and his main function is to bring prey, which he provides well in excess of the immediate requirements of the female and the chick. During the first month a parent is at the nest 85-95% of the time. 


At five weeks feathers are breaking on the scapulars and wing coverts, and first tail feathers appear. From six weeks on, it develops very rapidly until feathers cover the down at the age of eight weeks.  It first stands when about a month old, and tries unsuccessfully to feed itself, which it can only achieve at the age of six weeks. However, because of the tough nature of its staple diet, the female continues to tear open carcasses, as well as to feed it, until end of the nestling period. Although it attempts some wing flaps as early as two weeks, proper wing exercises only take place once it is feathered, increasing in frequency at the end of the nestling period. In the second stage, the female leaves the eaglet alone for progressively longer periods. Even in the exposed site it no longer needs shading, once it is about six weeks old. The female now also hunts actively, and continues to tear up prey for her offspring. The adults bring in birds plucked and hyraxes partially plucked. The nest is kept clean by the removal of bones and dry pieces of skin, and both sexes bring fresh lining, although not after two months. During the second month, a parent may be at the nest 50-55% of the time.


Parental attention in the nestling period is linked to three main stages of the eaglet’s development, which may be divided into its downy first month, the second month during which it becomes fully feathered, and the third period up to the time of its first flight. In the final stage parental time on the nest is mainly spent in delivering prey. During the third and final month, a parent may be at the nest for 10-15% of the time.


The juvenile first flies when between 90 and 98 days old, although it can leave the nest at 80 days if disturbed. Extensive personal observation is indicative that males usually fledge between 90-95 days whilst the heavier female fledges between 95-100 days occasionally observed fledging on 104 days. Males may however fledge sooner as was the case with “Witsie” who fledged at 86 days.  Males are smaller and lighter by weight than the females.

Its first flight is usually made independent of the adults’ presence; one flew 80m to an outcrop where it remained perched for a very long period of time. In its first month the juvenile is not adept at flying, in fact, it flies very little, spending much of its time on the nest where it roosts or on nearby perches and rocky outcrops. 

In its second month it becomes more accomplished on the wing and more adventurous, exploring and expanding its range, as well as occasionally accompanying its parents for short distances. At night it continues to roost on the nest.

During its third month out of the nest the juvenile wanders further afield, often well out of sight of the nest. It begins to snatch up items such as a spray of leaves and flying with it in its talons; this behaviour is linked to its increasing dexterity on the wing and serves as mock killing practice. It rarely visits the nest in daytime, although roosting on the nest or on perches in the area. Towards the end of the post-nestling period of three months the parents begin to chase it away.  

Post Fledging  

Throughout the post-nestling period the juvenile is fed regularly by the adults, and can always be located by its noisy cries of solicitation whenever it sees them. During the first month prey is brought to the nest, after which it’s normally delivered at various other perches, although the juvenile may still carry the prey to the nest and feed on it there. If it does not finish a meal, the female will feed on what is left, but the young bird is fed preferentially. It flies about very little with its parents, never accompanying them on hunting flights, and by the time it leaves the territory has yet to hunt and kill for itself.  In one study it was estimated that the adults and their eaglet accounted for about 236 hyraxes from hatching until the independence of the juvenile after a thirteen-week post-nestling period.

Once driven out of the territory the juveniles wander, or are harried by neighbouring pairs, until they reach a peripheral neutral zone or “empty quarter”, juveniles also group together and are referred to as floaters. . Ringed juveniles have been recovered at distances of 40, 72 and 176 km from their nest sites during the first year. 

Some of the predators on Verreaux’s eagle nestlings are baboons, crows, possibly pythons, leopards, caracal and small predatory mammals such as genets. 

As only a low 20-30% of the juveniles survive during their first year, mortality is a major cause in the demise of young birds of prey and includes:

  • Inability to hunt successfully,
  • Drowning in partially full/empty farm dam reservoirs,
  • Scavenging on poisoned carcasses,
  • Feeding on road kills and run over by truckers,
  • Colliding with overhead power cables maiming or be killed outright.


  • Basic Breeding Information

    A breeding season can be categorized into seven stages: 

    Nest refurbishment /Mating – March/April

    Egg laying – April/May

    Incubation – 44/5/6 days, April to June

    Hatching & Sibling Aggression – up to 7 days

    Nestling – 86 to 100 days, September

    Fledging – August/September 

    Ousting November/December  

    It is of utmost importance that your observations of the eagle’s crops, and prey status is correct at all times.

    Prey variation may consist of hyrax, red rock rabbit, scrub hare, guinea fowl, francolin, mongoose and the occasional monkey.  

    NB – the eagles do not prey on domestic dogs, cats and chickens. Any person who conveys this kind of information to anyone will be severely reprimanded as it may be detrimental to the eagles’ livelihood!!


Verreaux’s eagles’ nest sites

Verreaux’s eagles’ nest sites

Generally nest sites are in inaccessible habitat, has ensured that this eagle, though often persecuted by farmers, has most recently shown a steady decline in areas where previously pairs were observed to be frequent visitors. Throughout its range it occurs in rocky or mountainous terrain, but the environment may vary from semi-arid to areas of high rainfall. 

Over the years, nests have also been constructed in large trees such as eucalypt spp and pine spp as well as a baobab, on the ground, in power pylons and concrete microwave towers even on top of the telephone pole nests of sociable weavers.  Invariably, its presence almost always coincides with that of its principle prey, the hyrax. 

At MF, the ANP is the first known of nesting site purposely designed and constructed for this eagle species and as far as we are aware, it is a first for Africa. Not ideal in any way, as it offers no natural shade during the incubation period and when there is a chick growing up to juvenile stages, but during these instances, the female will provide shade on hot days. During the shade offering period and especially on hot windless days, one will observe that the adult/chick/juvenile is panting, with its beak slightly open; they will let air flow over their tongue to allow salivation to occur. 


Courtship displays are similar to the territorial displays performed throughout the year and are done singly or by the pair. Spectacular, steep, undulating dives are executed. At the top of the upward swoop the bird turns sideways or somersaults and rolls into the next dive with wings held against the body. On the upward swoop, and during the turn at the top, the white back shows conspicuously as the wings are opened. In a different display performed exclusively for courtship the male flies behind the female with his wings curved up above his back in a more exaggerated position than during normal soaring; he draws near her she may half roll and present her claws. Tumbling flights with interlocked claws are probably not a part of courtship and may be instances of occasional aggressive interactions with intruders.

Mating usually takes place on a favourite branch or rock perch near the nest, to the accompaniment of calling and rustling of feathers soon after. Mating may last between four and twenty-one seconds and can be performed 3 to 4 times per morning. 

Nest Building

Building a new nest from scratch may take an adult pair anything between six to eight weeks and such an activity will commence in early February and be complete by at least end March should they want to breed in that year. Once eagles have begun building, there is little chance in stopping them as they are on a mission to complete the structure and be certain that it is secure and that it will withstand the prevailing elements. Building a nest on a sturdy base such as a flat rock surface and or a platform such as the ANP, the chances of structural failure is greatly reduced, whereas building a nest in a tree is far more difficult as the supportive structure beneath the nest will have to carry the increased weight load of annual nest refurbishment.

Structural strength and stability thus play a large role in successful breeding and although some nests may increase to in excess of 4m tall, it will become precarious over time and it may topple over with a possible loss of life and or permanent injury to the birds. At Roodekrans during the no breeding event of 2016, during a heavy storm and high wind spell, the nest height was reduced by about 2m in height, which equates to about 4 to 6 years of bygone breeding seasons, quite a substantial amount of lost material.   

At the old pylon nest, the structure was and still is incredibly secure hence the fact that the eagles decided to build their nest within the first tier. By no means a safe site considering that 210KV of electricity passes in one end, is then bridged by very heavy cabling that projects 5m from the pylon under which the eagles fly to alight the nest…a very precarious and dangerous past time especially for young inexperienced juveniles to fledge and alight from. 

In 2009, whilst the ANP lay on the ground in two segments, Philip Tarboton, Teresa Moore and I built a new nest for the eagles that only took us two hours to construct complete with nesting cup that was lined with green leafy sprays, and tied to the basket structure with cable ties to prevent it disintegrating upon hoisting. When the eagles eventually took to –and liked the new nest, they brought additional nesting material to suit them and their comfort and whilst Teresa and I observed almost 12 hours 7 days per week!

We did notice that there was quite a sway in the mast and that the nest moved at least 15-25cm from side to side…enough to cause me considerable dizziness. Long story shortened, the breeding season was unsuccessful and both eggs addled, with the female aborting incubation after sixty days. 

Unfortunately we could not retrieve the eggs in time so that we could send them to Onderstepoort Veterinary School for an autopsy; the crows had already gotten to the eggs eating the contents thereof. Devastated, but willing to understand and learn from the failure, we had a meeting with Toni Niemand of Siyavaya Highway Construction JV and requested that the group add a cat ladder to the mast in an effort to stabilize the movement. Fortunately, the JV agreed to our proposal and by end February 2010 the contraption was lifted with a cherry picker and bolted to the mast with a specialist fixing bracket. The sheer weight of the additional 1.5 ton structure secured the mast adequately and we were finished just in time for the eagles’ return and their commencement of refurbishing the nest. Equally delighted that the eagles decided to return to the ANP and not rebuild the pylon nest, was immensely appreciated and we believed that they were showing us their appreciation for our consideration in a combined effort to secure their nesting site from swaying and unwarranted intruders.

Leafy Sprays

After the completion of stick refurbishment, green leafy sprays are brought to the nest to soften and line the 30-40cm round cup and if the eagles are going to spend 44 or 46 days incubating, they may as well be comfortable! Repair of an established nest takes about one month. Sprays brought to the nest sporadically by both sexes, frequently when relieving the partner at the nest. It is believed that apart from the comfort of using leafy sprays is that some species may inhibit medicinal values that reduce bugs and flies on the nest. At the ANP most sprays is from the rhus spp. whilst eucalypt and cabbage tree leaves are also used.