Day: May 10, 2014

Secretary Bird (Sagittarius serpentarius)

Secretary Bird (Sagittarius serpentarius)

The Secretarybird or Secretary Bird (Sagittarius serpentarius) is a very large, mostly terrestrial bird of prey. Endemic to Africa, it is usually found in the open grasslands and savannah of the sub-Saharan region. Although a member of the order Accipitriformes, which also includes many other diurnal raptors such as kites, buzzards, vultures, and harriers, it is given its own family, Sagittariidae. It appears on the coats of arms of Sudan and South Africa.

The Secretarybird is instantly recognizable as having an eagle-like body on crane-like legs which increases the bird’s height to as much as 1.3 m (4 ft) tall. This bird has an eagle-like head with a hooked bill, but has rounded wings. Body weight can range from 2.3 to 4.6 kg (5.1 to 10.1 lb) and height is 90–137 cm (35–54 in). Total length from 112 to 152 cm (44 to 60 in) and the wingspan is 191–220 cm (75–87 in). The tarsus of the secretarybird averages 31 cm (12 in) and the tail is 57–85 cm (22–33 in), both of which factor into making them both taller and longer than any other species of raptor. The neck is not especially long, and can only be lowered down to the inter-tarsal joint, so birds reaching down to the ground or drinking must stoop to do so.

From a distance or in flight it resembles a crane more than a bird of prey. The tail has two elongated central feathers that extend beyond the feet during flight, as well as long flat plumage creating a posterior crest.[9]Secretarybird flight feathers and thighs are black, while most of the coverts are grey with some being white. Sexes look similar to one another as the species exhibits very little sexual dimorphism, although the male has longer head plumes and tail feathers. Adults have a featherless red face as opposed to the yellow facial skin of the young.

Secretarybirds are endemic to Sub-Saharan Africa and are non-migratory, though they may follow food sources. Their range extends from Mauritania to Somalia and south to the Cape of Good Hope.[9] These birds are also found at a variety of elevations, from the coastal plains to the highlands. Secretarybirds prefer open grasslands and savannas rather than forests and dense shrubbery which may impede their cursorial existence. While the birds roost on the localAcacia trees at night, they spend much of the day on the ground, returning to roosting sites just before dark.

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, mammalsranging in size from mice to hares and mongoose, crabs, lizards, snakes, tortoises, young birds, bird eggs, and sometimes dead animals killed in grass or bush fires. Larger herbivores are not generally hunted, although there are some reports of Secretarybirds killing young gazelles. 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 snake preyed upon.

Prey is often discovered by the Secretarybirds via stomping on clumps of vegetation, which then flushes prey for them to capture. It also waits near fires, eating anything it can that is trying to escape. They can either catch prey by chasing it and striking with the bill and swallowing (usually with small prey), or stamping on prey until it is rendered stunned or unconscious enough to swallow.[9] Studies of this latter strategy have helped reconstruct the possible feeding mechanisms employed by the gigantic ‘terror birds’ that lived between sixty and five million years ago.[19]Larger or dangerous prey, such as venomous snakes, are instead stunned or killed by the bird jumping onto their backs, at which point they will try to snap their necks or backs. There are some reports that, when capturing snakes, the Secretarybirds will take flight with their prey and then drop them to their death, although this has not been verified. Even with larger prey, food is generally swallowed whole through the birds’ considerable gape. Occasionally, like other raptors, they will tear apart prey with their feet before consuming it.

Young are fed liquefied and regurgitated insects directly by the male or female parent and are eventually weaned to small mammals and reptile fragments regurgitated onto the nest itself. The above foodstuffs are originally stored in the crop of the adults.

In hunting and feeding on small animals and arthropods on the ground and in tall grass or scrub, Secretary Birds occupy an ecological niche similar to that occupied by peafowl in South and Southeast Asia, roadrunners in North andCentral America and seriemas in South America.

Secretarybirds often use kicks to incapacitate and kill their prey, with the bird’s sharp claws piercing the victim’s body. Their kicks are incredibly powerful; they are capable of shattering a human’s hand with a single kick.

Secretarybirds associate in monogamous pairs. 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 grounded display by chasing each other with their wings up and back, much like the way they chase prey. They usually mate on the ground, although some do so in Acacia trees. Secretarybirds will stay close to their mate even if their chick has already left.

Nests are built at a height of 5–7 m (15–20 feet) on Acacia trees. Both the male and female visit the nest site for almost half a year before egg laying takes place. The nest is around 2.5 m (eight feet) wide and 30 cm (one foot) deep, and is constructed as a relatively flat basin of sticks.

Secretarybirds lay two to three oval, pale-green eggs over the course of two to three days, although the third egg is most often unfertilised.[citation needed] These eggs are incubated primarily by the female for 45 days until they hatch. The Secretarybirds are facultatively fratricidal. There are conflicting opinions on this phenomenon also called cainism—”No evidence [exist] of sibling aggression, but youngest in brood of 3 almost always dies of starvation…”

The downy young can feed autonomously after 40 days, although the parents still feed the young after that time. Both the parents feed the young. At 60 days, the young start to flap their wings, and by day 65–80 are able to fledge. Fledging is accomplished by jumping out of the nest or using a semi-controlled fall via fervent wing flapping to the ground. After this time, the young are quickly taught how to hunt through expeditions with their parents and are considered independent soon after.