The Kori Bustard (Ardeotis kori) is a large bird native to Africa. It is a member of the bustard family. It may be the heaviest bird capable of flight.
Female, Serengeti. Tanzania
Distribution
The Kori Bustard is found throughout southern Africa, except in densely wooded areas. They are common in Botswana, Namibia, southern Angola, locally in Zimbabwe, marginally in southwestern Zambia, southern Mozambique and eastern South Africa. A geographically disjunct population also occurs in the deserts and savanna of northeastern Africa. Here, the species ranges from extreme south Sudan, north Somalia, Ethiopia through all of Kenya(except coastal regions), Tanzania and Uganda. They are usually residential in their range, with some random, nomadic movement following rainfall.
Habitat
This species occurs in open grassy areas, often characterized by sandy soil and short grasses. It may be found in plains, karoo, highveld grassland, arid scrub, lightly wooded savanna, open dry bushveld and semi-desert. They follow fires or herds of foraging ungulates, in order to pick their various foods out of the short grasses. They may also be found in cultivated areas, especially wheat fields with a few scattered trees. Most nests are found in sparsely wooded savanna with sparse grass cover.
Description
The Kori Bustard is cryptically colored, being mostly grey and brown in color, finely patterned with black and white coloring. The ventral plumage is more boldly colored, with white, black and buff. The crest on its head is blackish in coloration, with less black on the female's crest. A black collar at the base of the hind-neck extends onto the sides of the breast. The feathers around the neck are loose, giving the appearance of a thick neck. The belly is white and the tail has broad bands of brownish-gray and white coloration. The head is large and the yellow legs are relatively long. Females are similar in plumage but are much smaller, often weighing 2-3 times less than the male. The juvenile is similar in appearance to the female, but are browner with more spotting on the mantle.
A close-up of the plumage
The male Kori Bustard is 120 to 150 cm (3.9 to 4.9 ft), stands 71–120 cm (2.33–3.9 ft) tall and have a wingspan about 230 to 275 cm (7.5 to 9.02 ft). On average, male birds weigh between 10.9–16 kg (24–35 lb), averaging 13.5 kg (30 lb) but exceptional birds may weigh up to 20 kg (44 lb). Reports of outsized specimens weighing 23 kg (51 lb), 34 kg (75 lb) and even 40 kg (88 lb) have been reported, but none of these giant sizes have been verified and some may be from unreliable sources. Among bustards, only male Great Bustards achieve similarly high weights, making the male Kori and Great not only the two largest bustards, but also arguably the heaviest living flying animals. The female Kori Bustard weighs an average of 4.8 to 6.1 kg (11 to 13 lb), with a range of 4.3 to 6.6 kg (9.5 to 15 lb). Female length is from 80 to 120 cm (2.6 to 3.9 ft) and they usually stand less than 60 cm (2.0 ft) tall and have a wingspan of less than 220 cm (7.2 ft). The wing chord can measure from 58.5 to 83 cm (23.0 to 33 in), the tail measures from 30–45 cm (12–18 in), the culmen from 7 to 12.5 cm (2.8 to 4.9 in) and the tarsus from 16 to 24.5 cm (6.3 to 9.6 in). Body size is generally greater in the populations of southern Africa and body mass can vary based upon rain conditions.
Behavior
Kori Bustards spend most of their time on the ground, though can forage occasionally in low bushes and trees. Being a large and heavy bird, it avoids flying if possible. This bustard is a watchful and wary bird. Their behavior varies however, and they are usually very shy, running or crouching at the first sign of danger; at other times they can be completely fearless of humans. This large bird has a loud, booming mating call which is often uttered just before dawn and can be heard from far away. Locally, they are regularly found with bee-eaters riding on their backs as they stride through the grass. The bee-eaters make the most of their walking perch by hawking insects from the bustard's back that are disturbed by the bustard's wandering.
Voice
The male's mating call a deep, resonant woum-woum-woum-woum (Ginn et al 1989) or oom-oom-oom (Sinclair & Ryan 2003) or wum, wum, wum, wum, wummm (Newman 1992). This call ends with the bill snapping which is only audible at close range. They also utter aca-caa-ca, repeated several times for up to 10 minutes. This call carries long distances. Outside of the breeding display, Kori Bustards are often silent. A high alarm call, generally uttered by females, is sometimes heard. They utter a deep vum on takeoff.
Socialty
During the mating season, these birds are usually solitary but for the breeding pair. Otherwise, they are somewhat gregarious, being found in groups often including 5 to 6 birds but occasionally groups can number up to 40 individuals. Larger groups may found around an abundant food source or at watering holes. In groups, birds are often fairly far apart from each other, often around a distance of 100 m (330 ft). Interestingly, foraging groups are often single-sex. Such groups do not last long and often separate after a few days. These groups are believed to advantagous both in that they may insure safety in numbers against predation and may bring bustards to prime food sources.
Feeding
Walking slowly and sedately, they forage by picking at the ground with the bills and are most active in the first and last hours of daylight. Kori Bustards are quite omnivorous birds. Insects are an important food source, with common species such as locusts, grasshoppers,dung beetles and caterpillars being most often taken. They may follow large ungulates directly to catch insects flushed by them or to pick through their dung for edible invertebrates. During outbreaks of locusts and caterpillars, Kori Bustards are sometimes found feeding on them in numbers. Other insect prey can include bush-crickets, termites, hymenopterans and solifuges.Scorpions and
molluscs may be taken opportunistically as well.Small vertebrates may also been taken regularly, including lizards, chameleons, snakes, small mammals and bird eggs and nestlings. They may occasionally eat carrion, especially those killed in veld fires. Plant material is also an important food. Grasses and their seeds are perhaps most prominent, but they may also eat seeds, berries, roots, bulbs, flowers, wild melons and green leaves. This bustard is very partial to Acacia gum (Ginn et al 1989). This liking has given rise to the Afrikaans common name Gompou or, literally translated, "gum peacock". They drink regularly when they can access water but they can found far from water sources. Unusually, they suck up rather than scoop up water.
Breeding
The breeding season is between October and March, though mainly November and December. Like all bustards, Kori Bustards have polygynous breeding habits, where one male displays to attract several females and mates with them all. Male Kori Bustard displays on a lek. The males hold their heads backwards, with cheeks bulging, the crest is held erect, the bill open and they inflate their gular pouches, forming a white throat "balloon". During this display the oesophagus inflates to as much as four times its normal size and resembles a balloon. They also puff out their frontal neck feathers which are splayed upwards showing their white underside. Their wings are drooped and their tails are raised upwards and forwards onto their backs like a turkey, the retrices being held vertically and their undertail coverts fluffed out. They enhance their performance with an exaggerated bouncing gait. When displaying they stride about with their necks puffed out, their tail fanned and their wings planed and pointed downward. They also emit a low-pitched booming noise when the neck is at maximum inflation and snap their bills open and shut. Occasionally fights between males can be serious, with the two competitors smashing into each other's bodies and stabbing each other with their bills.
Following the display, the copulation begins with the female lying down next to the dominant displaying male. He stands over her for 5-10 minutes, stepping from side to side and pecking her head in a slow, deliberate fashion, tail and crest feathers raised. She recoils at each peck. He then lowers himself onto his tarsi and continues pecking her until he shuffles forward and mounts with wings spread. Copulation lasts seconds after which both stand apart and ruffle their plumage. The female then sometimes barks and the male continues with his display.
The female Kori Bustard lays her eggs on the ground in a shallow, unlined hollow, rather than a scrape. This nest is usually located within 4 m (13 ft) of a tree or shrub, termite mound or an outcrop of rocks. Usually two eggs are laid, though seldomly 1 or 3 may be laid. They are cryptically colored with the ground color being dark buff, brown or olive and well marked and blotched with shades of brown, grey and pale purple. Egg size is 83 mm (3.3 in)x60 mm (2.4 in) mm. and weigh about 146 g (5.1 oz). The female, who does all brooding behavior alone without male help, stays at the nest 98% of the time, rarely eating and never drinking. The incubation period is 23 to 30 days. The young are precocial and very well camouflaged. When the chicks hatch, the mother brings them a steady stream of food, most of it soft so the chicks can eat it easily.After a few weeks, the young actively forage closely with their mothers. They fledge at 4 to 5 weeks old, but are not self-assured fliers until 3 to 4 months. On average, around 67% of eggs successfully hatch (testimony to the effective camoflauge of nests) and around one of the two young survive to adulthood.
Predation
Being a large, ground-dwelling bird species, the Kori Bustard is vulnerable to many of Africa's myriad of terrestrial predators. Leopards,caracals, cheetahs, lions, rock pythons, jackals and Martial Eagles (the latter two especially of eggs and nestlings) have eaten bustards of all ages. Additionally, warthogs, mongooses and baboons may eat eggs and nestlings.
Status
The Kori Bustard is generally a somewhat scarce bird. In protected areas, they can be locally common. They have been much reduced by hunting, having been traditionally snared in Acacia gum baits and traps. Although no longer classified as game birds, they are still sometimes eaten. Hunting of bustards in difficult to manage. Habitat destruction is a major problem for the species, compounded by overgrazing by livestock. Poisons used to control locusts may also effect and collisions with power wires regularly claim Kori Bustards.
