Secretarybird

The Secretarybird is a monogamous bird which can reproduce all year round. A peak is nonetheless observed between August and March over the whole of the Zambia area. The couple generally frequents the same nest for several years. It is built, by both partners, generally at a height between 3m and 7.5m at the top of an acacia or spiny tree (in South Africa, isolated pine trees are also used). It is 1.5m to 2.5m in diameter and has an approximate depth of 30 to 50 cm. It is made up of branches and twigs and is lined with grass and mammal hair. This last layer is renewed with each nesting. When the weight of the building becomes too much and threatens the stability of the support, it is abandoned.
During the nuptial period, the couple performs flights of parade quite similar to those of other raptors. Thus they can make circles at different altitudes. The male also flies in an acrobatic and undulating manner; he can fly up to a high altitude to plunge suddenly towards the female who turns around and presents her claws to him. On the ground, the parades are very similar to those of cranes; both birds parade with wings spread, up and back, in a posture reminiscent of that adopted during the hunt.

The mating usually takes place on the ground, but can sometimes take place on an acacia tree.
The incubation lasts from 42 to 46 days and is shared by the male and the female, the latter usually undertaking this task. During this period the male brings food to the nest.
She lays one to three eggs (often two), whitish-gray with reddish-brown marbling. The layings are spaced two to three days apart. The third egg, when it exists, is rarely fertilized.
If it manage to hatch, the probability that the chick dies of inanition is very important.Indeed, it can't compete with the rest of the clutch which is older. The chicks are covered in white down and have a head that seems disproportionate to the rest of the body. At the age of two weeks, they become gray and at three weeks the crest begins to appear. Both parents feed them by regurgitation and give them constant care for the first 40 days. At this stage, they are able to feed themselves. The adults then become less present, only going to the nest to bring them food. After six weeks, they stop regurgitating food and bring whole prey which they give directly to the chicks. Around 60 days, the chick starts to beat its wings, and will leave the nest shortly after. It acquires the adult plumage at a very variable age (from 64 to 106 days).
The juveniles then leave the nest but stay close by. They follow the parents in their search for food and are thus initiated into the hunting techniques. Once autonomous, they leave the parents' territory. However, they are sometimes tolerated until the adults chase them for another nesting.
When conditions are favorable, the Secretarybird can have a clutch every ten months. It is when they are in the nest that the young are most vulnerable and exposed to predation. These are often perpetrated by crows, birds of prey (for example Greater Spotted Eagle, kite) or hoatzins (Southern Ground-Hornbill). (Steyn, 1983)
In Southern Africa, the most favorable region for the species, the territory of a couple varies a lot; it ranges from 20 to 230 km², with a proximity between the nests that ranges from 4 to 15 km. Rarer elsewhere in the continent, the Secretarybird's territory covers an area of about 500 km².