Verreaux’s eagles’ breeding
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.
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.
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.
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
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!!