Secretary birds prefer open savannahs and grasslands, although they also live in semi-deserts and lightly wooded or scrub areas. In grasslands, secretary birds choose areas where the grass is one meter or less in height so their view is not obstructed. They are common near agricultural areas that offer hunting opportunities. Secretary birds are never found in true deserts with extreme aridity, or heavily wooded areas. These birds are found from sea-level to around 3,000 m. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Steyn, 1983)
Secretary birds stand around 0.9 to 1.2 meters tall and weigh between 2.3 to 4.27 kg. Females tend to be slightly smaller than males. Wingspans of females range from 1.2 to 1.32 m, while those of males range between 1.26 to 1.35 m. (Ferguson-Lees and Christie, 2001; Mackworth-Praed and Grant, 1980)
These large raptors have very distinctive morphology. The plumage is generally gray in color, perhaps with some white feathers. They have black flight feathers on the wings and a crest of black-tipped feathers on the back of the head. The bare face is orange to red in color. They have a relatively small head, a gray-white beak, a long neck, and an eagle-like body. Unlike an eagle, however, the bare, pinkish legs are very long and end in stubby toes with blunt claws. The tibial portions of the legs are covered in black plumage that give the bird the appearance that it is wearing shorts. The long tail has especially long central rectrices that are often tipped with black. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Mackworth-Praed and Grant, 1980; Steyn, 1983)
It would be hard to confuse bustards or cranes. They are perhaps most commonly mistaken for blue cranes (Anthropoides paradiseus). (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Steyn, 1983)with any other bird of prey, mainly due to their very long legs. From a distance secretary birds are mistaken for
Secretary birds are monogamous and are thought to pair for life. In courtship, they give a croaking call while displaying in the air and on the ground. Aerial displays consist of high soaring and diving performed by a single individual (usually the male), or by the pair when the male will dive toward the female and she will half-turn to present her claws. This courtship behavior is very similar to that of other birds of prey. On the ground, their displays are very crane-like with the two birds dancing around with their wings outstretched. Sometimes small groups of secretary birds will all join in this ground display behavior. After courtship displays, mating will usually take place on the ground, although some pairs mate in trees. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Steyn, 1983)
The female lays a clutch of 1 to 3 eggs, with each egg laid two to three days apart. The eggs are chalky-white with reddish-brown streaks and are pyriform in shape. Eggs are variable in size and can range from 68 to 92 mm in length and 52 to 61 mm in width. Incubation of the eggs begins as soon as the first egg is laid. Incubation duties are shared by both the male and female, although more frequently by the female. The male brings food to the nest for the female during this time. In 42 to 46 days, the semi-altricial young hatch. Young generally hatch 2 to 3 days apart, but no siblicide has been observed. However, in a clutch of three eggs, the smallest chick usually dies of starvation because it cannot compete with its larger nest mates. (Ferguson-Lees and Christie, 2001; Mackworth-Praed and Grant, 1980; Steyn, 1983)
Hatchlings are covered in off-white down and have large heads that seem too heavy for their bodies. At two weeks of age, they attain a thick coat of gray down, and in three weeks the crest begins to appear. Development is slow in secretary birds and it takes six weeks before the hatchlings can stand on their own. At this stage, they learn to feed themselves from prey brought to the nest. By seven weeks, nestlings are fully feathered. Around 60 days, the young begin flexing their wings, often flapping and lifting small distances into the air before dropping back to the nest. In 64 to 106 days, the offspring will fledge. The offspring remain around the nest tree for an additional 62 to 105 days, during which time they are dependent upon the parents for food and training in foraging techniques. (Ferguson-Lees and Christie, 2001; Steyn, 1983)
Both male and female secretary birds invest heavily in the young. Both sexes share incubation duties. After the eggs hatch, parental care is constant. Both the male and female feed the young via regurgitation, although the female mostly regurgitates food that the male has brought back to the nest for her. After about a month, parental care drops significantly, with the parents only returning to the nest to feed the chicks. After six weeks, the parents stop feeding via regurgitation and bring larger prey items that they give the chicks to eat directly. When the chicks fledge and leave the nest, the parents will teach the chicks how to hunt for prey. Once the offspring know how to provide for themselves and are independent, they generally head off on their own, leaving the parents’ territory. However, in some circumstances the parents will still tolerate having the juveniles in their territory and even allow the now-independent offspring to join in their hunts and share the nest tree as a roost. It is important to note that juveniles are not dependent on the parents during this time. They are just temporarily sharing a territory. Two months is the average amount of time that independent juveniles are allowed to remain in the parents’ territory before being chased away so that the parents can breed again. (Hosking, et al., 1988; Steyn, 1983)
The lifespan ofis currently unknown and further study is required.
A pair of secretary birds defends an area that can range from 20 to 500 square kilometers depending on the density of secretary birds and food resources in the area. Any conspecifics caught intruding in a pair's territory will be chased out forcefully. (Ferguson-Lees and Christie, 2001; Steyn, 1983)is generally sedentary and will remain in its own territory, but they are sometimes nomadic. In most cases, these nomadic tendencies are caused by a search for food.
Secretary birds are generally silent. When they do call, they typically give a deep, trisyllabic croaking wail that can be heard for quite some distance. This call, along with a drawn-out growling sound, is used in conjunction with aerial and ground displays during the courtship process. A softer version of the main call is used when feeding young. An occasional whistle is given from time to time. The young have their own calls to solicit food from their parents, which start off as a quiet squealing, then becoming a loud 'chok-a-chok-a-chok-a-chok'. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Mackworth-Praed and Grant, 1980; Steyn, 1983)
Secretary birds hunt exclusively on the ground, either alone or in pairs (usually with their mate). The birds will set out across a grassy area at a steady pace searching for movement. If a particularly thick tuft of grass is encountered, the bird will stamp on it to flush out any potential prey. Once prey is spotted, the bird quickens its pace to take the prey by surprise. If a chase commences, the bird will flap its wings and run after the prey until catching up to it. With small prey, the bird will merely bend down and capture it in its bill. Larger prey, especially snakes, are stamped to death with the bird's blunt feet. A secretary bird will strike a snake just behind its head to snap its neck or stun it. Secretary birds are said to pick up a stunned snake, fly high into the air and drop the snake to its death, but this behavior has not been well documented. Once the prey is stunned or killed, the bird will swallow it whole through its large gape. If the prey proves too large, then the bird will tear it apart much like an eagle, using its feet to hold the prey down. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Steyn, 1983)
Secretary birds regurgitate pellets after the prey is digested. The pellets consist of fur, bones, and invertebrate exoskeletons. Sometimes grass is found in the pellets. It is unknown whether the birds swallow grass incidentally along with the prey, or if they swallow it intentionally to help hold the pellet together when there is little fur present. Stones, which are swallowed to help in breaking up the exoskeletons of larger invertebrates, have also been found in the pellets. Secretary bird pellets are found around and in the nest and are especially helpful to researchers in analyzing the diet of birds in that area. (Steyn, 1983)
Secretary birds are generally only vulnerable to predation as eggs and young birds in the nest. Their large, open nests leave the nestlings vulnerable to predation by crows, ravens, ground hornbills and birds of prey, such as kites or eagle-owls. (Steyn, 1983)
These birds prey on a wide range of large invertebrates and small to medium-sized vertebrates, but do not seem to have a great overall effect on these populations in the wild. Smaller, localized populations may be affected by predation from this species if hunting increases, especially during breeding season.
The vulnerable nestlings of secretary birds are occasionally taken as food by a number of predators. However, the low density of secretary bird nests means they are not vital to the predators' diets, and they have little effect on their survival. (Ferguson-Lees and Christie, 2001; Steyn, 1983)
There are no known adverse effects ofon humans.
The origin of the common name may come from the fact that their crest feathers made these birds look like old-time secretaries who used to keep their quill pens tucked behind their ears. In recent years, however, this has been challenged. It is instead thought by some that the name comes from the Arabic 'saqr et-tair'. 'Saqr' means "hunter" or "hawk" and 'et-tair' means "flight" or, in general, "bird". Thus, 'saqr et-tair' might mean "hunter bird", which would be an appropriate name for this species given its feeding behavior. (Ferguson-Lees and Christie, 2001; Hosking, et al., 1988; Mackworth-Praed and Grant, 1980; Steyn, 1983)
Tanya Dewey (editor), Animal Diversity Web.
Patrick Sherman (author), Michigan State University, Pamela Rasmussen (editor, instructor), Michigan State University.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
Having one mate at a time.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
scrub forests develop in areas that experience dry seasons.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
breeding takes place throughout the year
Ferguson-Lees, J., D. Christie. 2001. Raptors of the World. New York: Houghton Mifflin Company.
Hosking, E., D. Hosking, J. Flegg. 1988. Birds of Prey of the World. Lexington, Massachusetts: The Stephen Greene Press.
Mackworth-Praed, C., C. Grant. 1980. Birds of Eastern and North Eastern Africa, Volume 1. New York: Longman Inc..
Steyn, P. 1983. Birds of Prey of Southern Africa: Their Identification & Life Histories. Dover, New Hampshire: Tanager Books, Inc..