The secretarybird or secretary bird (Sagittarius serpentarius) is a large bird of prey that is endemic to Africa. It is mostly terrestrial, spending most of its time on the ground, and is usually found in the open grasslands and savanna of the sub-Saharan region. John Frederick Miller described the species in 1779. A member of the order Accipitriformes, which also includes many other diurnal birds of prey such as eagles, hawks, kites, vultures, and harriers, it is placed in its own family, the Sagittariidae.
The secretarybird is instantly recognizable as a very large bird with an eagle-like body on crane-like legs that give the bird a height of as much as . The sexes are similar in appearance. Adults have a featherless, red-orange face and predominantly grey plumage, with a flattened dark crest and black flight feathers and thighs.
Breeding can take place at any time of year, but tends to be late in the dry season. The nest is built at the top of a thorny tree, and a clutch of one to three eggs is laid. In years with plentiful food, all three young can survive to fledging. The secretarybird hunts and catches prey on the ground, often stomping on victims to kill them. Insects and small vertebrates make up its diet.
Although the secretarybird resides over a large range, the results of localized surveys suggest that the total population is experiencing a rapid decline, probably as a result of habitat destruction. The species is therefore classed as endangered by the International Union for Conservation of Nature. The secretarybird appears on the coats of arms of South Africa and Sudan.
Taxonomy
Dutch naturalist Arnout Vosmaer described the secretarybird in 1769 on the basis of a live specimen that had been sent to Holland from the Cape of Good Hope two years earlier by an official of the Dutch East India Company. Vosmaer suggested that the species was called "sagittarius" by the Dutch settlers because its gait was thought to resemble an archer's. He also mentioned that it was known as the "secretarius" by farmers who had domesticated the bird to combat pests around their homesteads, and proposed that the word "secretarius" might be a corruption of "sagittarius". Contains eight pages and a plate. Contains eight pages and a plate. Ian Glenn of the University of the Free State suggests that Vosmaer's "sagittarius" is a misheard or mistranscribed form of "secretarius", rather than the other way around.
In 1779 the English illustrator John Frederick Miller included a coloured plate of the secretarybird in his Icones animalium et plantarum and coined the binomial name Falco serpentarius. As the oldest published specific name, serpentarius has priority over later scientific names. The species was assigned to its own genus Sagittarius in 1783 by the French naturalist Johann Hermann in his Tabula affinitatum animalium. The generic name Sagittarius is Latin for "archer", and the specific epithet serpentarius is from Latin serpens meaning "serpent" or "snake". A second edition of Miller's plates was published in 1796 as Cimelia physica, with added text by English naturalist George Shaw, who named it Vultur serpentarius. The French naturalist Georges Cuvier erected the genus Serpentarius in 1798, and the German naturalist Johann Karl Wilhelm Illiger erected the (now synonymous) genus Gypogeranus from the Ancient Greek words gyps "vulture" and geranos "crane" in 1811.
In 1835, Irish naturalist William Ogilby spoke at a meeting of the Zoological Society of London and proposed three species of secretarybird, distinguishing those from Senegambia as having broader crest feathers than those from South Africa, and reporting a distinct species from the Philippines based on the writings of Pierre Sonnerat in his Voyage à la Nouvelle-Guinée. There is no other evidence this taxon existed. Despite its large range, the secretarybird is considered monotypic: no subspecies are recognised.
The evolutionary relationship of the secretarybird to other raptors had long puzzled ornithologists. The species was usually placed in its own family, the Sagittariidae, within the order Falconiformes. A large molecular phylogenetic study published in 2008 concluded that the secretarybird was sister to a clade containing the ospreys in the family Pandionidae and the kites, hawks, and eagles in the family Accipitridae. The same study found that the falcons in the order Falconiformes were only distantly related to the other diurnal birds of prey. The families Cathartidae, Sagittariidae, Pandionidae, and Accipitridae were therefore moved from the Falconiformes to the resurrected Accipitriformes. A later molecular phylogenetic study published in 2015 confirmed these relationships.
The earliest fossils associated with the family are two species from the genus Pelargopappus. The species, from the Oligocene and Miocene, respectively, were discovered in France. The feet in these fossils are more like those of the Accipitridae; these characteristics are suggested to be primitive features within the family. In spite of their age, the two species are not thought to be ancestral to the secretarybird. Though strongly convergent with the modern secretarybird, the extinct raptor Apatosagittarius is thought to be an accipitrid.
The International Ornithologists' Union has designated "secretarybird" the official common name for the species. In 1780, French polymath Georges-Louis Leclerc, Comte de Buffon suggested that the name secretary/secrétaire had been chosen because of the long, quill-like feathers at the top of the bird's neck, reminiscent of a quill pen behind the ear of an ancient scribe. In 1977, C. Hilary Fry of Aberdeen University suggested that "secretary" is from the French secrétaire, a corruption of the Arabic saqr et-tair meaning either "hawk of the semidesert" or "hawk that flies". Glenn has dismissed this etymology on the grounds that no evidence supports that the name came through French, instead supporting Buffon's etymology, namely, that the word comes from the Dutch secretaris "secretary", used by settlers in South Africa.
Description The secretarybird is instantly recognisable as a very large terrestrial bird with an eagle-like head and body on crane-like legs. It stands about tall. It has a length of between and a wingspan between . Its weight ranges from , with a mean of . The averages and the tail is ; both factor into making it both taller and longer than any other species of raptor. The neck is not especially long, and can only be lowered down to the intertarsal joint, so birds must stoop to reach down to the ground.
During flight, two elongated central feathers of the tail extend beyond the feet, and the neck stretches out like a stork. The plumage of the crown, upperparts, and lesser and median wing coverts is blue-grey, and the underparts and underwing coverts are lighter grey to grey-white. The crest is made up of long, black feathers arising from the nape. The scapulars, primary and secondary flight feathers, rump, and thighs are black, while the uppertail coverts are white, though barred with black in some individuals. The tail is wedge-shaped with white tipping, marbled grey and black colouring at the base, and two broad, black bands, one at the base and the other at the end.
Sexes resemble one another, although the male tends to have longer tail feathers, more head plumes, a shorter head, and more blue-grey plumage. Adults have a featherless, red-orange face with pale brown irises and a yellow cere. The legs and feet are pinkish-grey, and the upper legs clad in black feathers. The toes are short—around 20% of the length of those of an eagle of the same size—and stout, so that the bird is unable to grasp objects with its feet. The rear toe is small and the three forward-facing toes are connected at the base by a small web. Immature birds have yellow rather than orange bare skin on their faces, more brownish plumage, shorter tail feathers, and greyish rather than brown irises.
Adults are normally silent, but can utter a deep, guttural, croaking noise in nuptial displays or at nests. Secretarybirds make this sound when greeting their mates or in a threat display or fight against other birds, sometimes throwing their head backwards at the same time. When alarmed, they may emit a high-pitched croak. Mated pairs at the nest make soft clucking or whistling calls. Chicks make a sharp sound heard as "chee-uk-chee-uk-chee-uk" for their first 30 days.
Distribution and habitat The secretarybird is endemic to sub-Saharan Africa and is generally nonmigratory, though it may be locally nomadic, as it follows rainfall and the resulting abundance of prey. Its range extends from Senegal to Somalia and south to Western Cape, South Africa.
The species is also found at a variety of elevations, from the coastal plains to the highlands. The secretarybird prefers open grasslands, savannas and shrubland (Karoo) rather than forests, and dense shrubbery that may impede its cursorial existence. More specifically, it prefers areas with grass under high and avoids those with grass over high. It is rarer in grasslands in northern parts of its range that otherwise appear similar to areas in southern Africa, where it is abundant, suggesting it may avoid hotter regions. It also avoids deserts. Behaviour and ecology
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. They set off 1–2 hours after dawn, generally after spending some time preening. Mated pairs roost together, but may forage separately, though often remaining in sight of one another. They pace around at a speed of , taking 120 steps per minute on average. After spending much of the day on the ground, secretarybirds return at dusk, moving downwind before flying in upwind. Birds encountered singly are often unattached males; their territories are generally in less suitable areas. Conversely, larger groups of up to 50 individuals may be present at an area with a localised resource such as a waterhole in a dry area or an irruption of rodents or locusts fleeing a fire.
Secretarybirds soar with their primary feathers splayed to manage turbulence. Their wings can flap, though in a slow, laborious manner and requiring uplift to be sustained; otherwise, they may become exhausted. In the heat of the day, they use thermals to rise up to above the ground.
The bird's average lifespan is thought to be 10 to 15 years in the wild and up to 19 years in captivity. The oldest confirmed secretarybird in the wild was a 5-year-old that was banded as a nestling on 23 July 2011 in Bloemfontein and recovered away in Mpumalanga on 7 June 2016.
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.