|Conservation status||Vulnerable (2011)|
The secretary bird (Sagittarius serpentarius) is a long-legged bird of prey inhabiting much of sub-Saharan Africa. The only living member of the family Sagittariidae, current scientific consensus places it within the Falconiformes, despite anatomical and superficial similarities shared with the South American cariamas.
The name is in reference to the sparse crest of feathers adorning the back of the head, after a passing resemblance to 18th century clerks who had goose-quill pens held behind their ears when not writing.
The secretary bird is a large raptor, often seen on the ground walking in a manner similar to cranes or bustards. It has a body length of 4.1 to 4.9 feet; a wingspan of 6 to 7 feet, and stands nearly 4 feet tall on crane-like legs. It is predominately gray, with black primaries and secondaries on the wings, black belly and thighs. The tail is long with black bars, with the two central tail feathers nearly twice as long as the others. In flight the secretary bird is almost unmistakable, giving the the appearance of a powerful hawk or eagle in front with long legs and tail of a crane trailing behind.
The relatively small head is eagle-like with quite large eyes and a hook-shaped, blue-gray beak, yellow waxy skin and a lively orange, bare skin around the eye. Unlike other birds of prey, the upper eyelids bare long eyelashes.
The neck plumage is characterized by a long and sparse crest of black-tipped feathers, placed on the upper back of the neck. The neck itself is moderately long, but not as long as cranes. Bending downwards the head can only reach midway down the legs; it cannot touch the ground without completely stooping. The long legs are 2 feet in length, feathered halfway in black, with the lower legs covered in strong, course scales. The toes are short and strong with equally short, downward-bending claws, which, in comparison with eagles of similar size, are only about one-fifth the length. Unlike eagles, the secretary bird can not grasp with its feet, but it kills prey with them just the same, by using lethal kicks and stomping.
Habitat and range
Secretary birds inhabit mainly open and semi-open savannah landscapes from sea level to 3,500 feet. Occasionally can be found on cereal crops and in semi-deserts with sparse vegetation. It is most common in relatively short-grass thorn-bush savannahs with scattered umbrella acacias that can serve as a sleeping place or nesting site. The preferred height of the grass is usually around 1.5 feet, with grassy locations shunned if the growth is three or more feet.
Its range extends over large parts of the African continent, with the species absent in the rainforest belt, the Horn of Africa and Madagascar. It extends from southern Mauritania, Senegal, Gambia and northern Guinea eastwards through Mali, Burkina Faso, Ghana, Togo, Benin, the southern regions of Niger, Chad, Sudan and the northern regions of Nigeria, Cameroon and the Central African Republic as far east as Ethiopia and to northwestern Somalia. Southwards it runs through the northeast and southeast of the Democratic Republic of Congo, through Uganda, Kenya and Tanzania as well as from Angola, Zambia, Malawi and Mozambique to the Cape of Good Hope.
The secretary bird feeds on small to medium sized prey animals, ranging in size from small insects to hares. In terms of numbers, insects such as beetles and grasshoppers represent the largest proportion of prey items taken; other animals include mice, hedgehogs, mongooses, meerkats, and hares; lizards, snakes, chameleons, small birds, and juveniles of larger species, such as ostriches and ducklings. The bird has not been seen to scavenge the carcasses of dead animals.
Prey animals are only searched for while the bird is on the ground, whereby the bird can walk between 12 to 18 miles per day, taking virtually all suitable prey animals that it can see. Sometimes it will pursue prey in short sprints, opening the wings halfway to keep his balance. It will kick at tufts of grass to flush out hiding animals, and has been observed near the edges of grass fires, taking advantage of fleeing animals.
Prey is killed with targeted kicks. Experiments with a captive bird showed that these kicks occur at a very high speed. The contact with the prey lasts 15 milliseconds - only one tenth of the time it takes to open and close a human eyelid - and is done with a force of 195 newtons, which corresponds to five times the body weight of the bird. Larger prey is sometimes held with one foot while stomped with the other and/or torn with the beak. Prey animals are consumed whole, with the indigestible portions (hair, bones, etc) regurgitated as pellets.