Secretarybirds are not generally
gregarious aside from pairs and their offspring. They usually
roost in trees of the genus
Acacia or
Balanites, or even introduced pine trees in South Africa. moving
downwind before flying in upwind. Secretarybirds, like all birds, have haematozoan blood parasites that include
Leucocytozoon beaurepairei (Dias 1954 recorded from Mozambique). Wild birds from Tanzania have been found to harbor
Hepatozoon ellisgreineri, a genus that is unique among avian haematozoa in maturing within
granulocytes, mainly
neutrophils. Ectoparasites include the lice
Neocolpocephalum cucullare (
Giebel) and
Falcolipeurus secretarius (Giebel).
Breeding Secretarybirds form
monogamous pairs and defend a large territory of around . They can breed at any time of the year, more frequently in the late
dry season. During
courtship, they exhibit a nuptial display by soaring high with undulating flight patterns and calling with
guttural croaking. Males and females can also perform a ground display by chasing each other with their wings up and back, which is also the way they defend their
territories. They mate either on the ground or in trees. The nest is built by both sexes at the top of a dense, thorny tree, often an
Acacia, at a height between above the ground. The nest is constructed as a relatively flat platform of sticks across with a depth . The shallow depression is lined with grass and the occasional piece of dung. The eggs hatch after around 45 days at intervals of 2–3 days. but if food is scarce one or more of the chicks will die from starvation.
Food and feeding Unlike most
birds of prey, the secretarybird is largely
terrestrial, hunting its prey on foot. Adults hunt in pairs and sometimes as loose familial flocks, stalking through the habitat with long strides. Prey may consist of insects such as
locusts, other
grasshoppers,
wasps, and
beetles, as well as
millipedes,
spiders,
scorpions, and
freshwater crabs, but small vertebrates often form their main biomass. Secretarybirds are known to hunt
rodents, frogs, lizards, small
tortoises,
eggs, and birds such as
warblers,
larks,
doves, small
hornbills, and
domestic chickens. They occasionally prey on larger mammals, such as
hedgehogs,
mongooses, small
felids such as cheetah cubs,
striped polecats, young
gazelles, and both young and full-grown
hares. The importance of snakes in the diet has been exaggerated in the past, although they can be locally important, and venomous species such as
adders and
cobras are regularly among the types of snakes preyed upon. Secretarybirds do not eat
carrion, though they occasionally eat dead animals killed in grass or bushfires. The birds often flush prey from tall grass by stomping on the surrounding vegetation. Their crest feathers may raise during a hunt, which may serve to help scare the target and provide shade for the face. The large intestine has a pair of vestigial
ceca as no requirement exists for the fermentative digestion of plant material. Secretarybirds specialise in stomping their prey until it is killed or immobilised. This method of hunting is commonly applied to lizards or snakes. An adult male trained to strike at a rubber snake on a force plate was found to hit with a force equal to five times its own body weight, with a contact period of only 10–15 milliseconds. This short time of contact suggests that the secretarybird relies on superior visual targeting to determine the precise location of the prey's head. Although little is known about its visual field, it is assumed to be large, frontal, and binocular. Secretarybirds have unusually long legs (nearly twice as long as other ground birds of the same body mass), which is thought to be an adaptation for the bird's unique stomping and striking hunting method. These long limbs, though, appear to also lower its running efficiency. Ecophysiologist Steve Portugal and colleagues have hypothesised that the extinct
Phorusrhacidae (terror birds) may have employed a hunting technique similar to secretarybirds because they are
anatomically similar, although they are not closely related. Secretarybirds rarely encounter other predators, except in the case of
tawny eagles, which
steal their kills. Eagles mainly steal larger prey and attack secretarybirds as both singles and pairs. Secretarybird pairs are sometimes successful in driving the eagles away and may even knock them down and pin them to the ground. Secretary bird (Sagittarius serpentarius) - Flickr - Lip Kee.jpg|In flight Sagittarius serpentarius (31035947287).jpg |In flight showing the long tail and legs Secretary_bird_D'Alton.jpg|Secretarybird skeleton: The feet are used for killing prey|alt=skeleton of long-legged bird of prey 20170525 Pairi Daiza Sagittarius serpentarius con huevos.jpg|Captive secretarybird with two eggs in its nest|alt=long-legged grey bird standing in large nest of sticks and grass Faune de la Sénégambie (Planche V) BHL34755809.jpg|Illustration of chick, from
Faune de la Sénégambie (1883), by
Alphonse Trémeau de Rochebrune|alt=line drawing of long-legged chick Sagittarius serpentarius -Namib-Naukluft National Park, Namibia -eating-8.jpg|Juvenile with lizard kill at
Namib-Naukluft National Park, Namibia|alt=brownish bird with small, dead lizard in its mouth == Relationship with humans ==