Struthio camelus (Ostrich)
Adult male Ostrich
Description: Huge, flightless, two-toed terrestrial birds, with a long powerful neck and legs. The head is rather small in relation to the body, it has huge eyes and a long black eyelashes.
Coat: The long neck and legs are nacked with some downy feathers on the head. Males have pink skin and females a light brown coloured skin with dusty brown feathers and brown or stained whitish flight and tail feathers. Males are black featherd with a white ring at the base of the neck and white tail and flight feathers. The down on the head is greyish white and they have blue eyes.
The males bare parts become brighter during the breeding season.
Adult female Ostrich
Size: Males: Total length 210-275cm. Females: Total length 175-190cm.
Weight: Males: 100-156 kg. Females: 90-110 kg.
Senses: The large eyesa re used to scan vast areas of their habitat in search of danger and at close range they can pick out small objects on the ground easily.
They can run at speeds of 50 km/h for about 30 minuets and can reach speeds of 70 km/h with 3.5 m strides for short bursts.
Ostriches an save a great deal of water by a special physiolaogical adaptation, whereby they can increase their body temperature by 4.2 degrees celceus on hot days, thus reducing water loss through transpiration.
Habitat: A variety of open, semi-arid plains, from desert to savanna; also in open woodlands. They genreally do not rely on standing water.
Range: Ostriches are gregarious, however the size and structure of the groups vary greatly, depending o nthe habitat and the time of year. Outwith the breeding season the group tends to consist of 2-5 birds, while single animals are also frequently seen. Alternatively a variable number of immatures and adults of both sexes join groups of up to 100 birds, in which individuals seem to come or go as they please. In the breeding season however, birds form pairs or small harems. Each groups has its own sites for feeding, roosting and dust-bathing, and they tend to avoid contact with other groups. However during the dry season in arid areas, the birds are forced by nessecity for water to form large groups with up to 680 birds, they join only to drink and split up again afterwards.
Males hold ranges of 2-15 km square and they patrol the area booming. On the approach of an individual, he will set off towards it in a dominat posture. If the bird is a male he will expel it, if it is a female he approaches until he is fairly close and then he suddenly flops down on the ground, opens his wings and begins to shake each wing alternately and move his tail up and down. Meanwhile, his head and neck sway from side to side beating against his flanks. After a while he gets up and walk to the female, with his wings open and his neck puffed out, stamping as he goes. Now, depending on her attitude, he either sits agian and repeats the display or he goes to mount her. Females show that they are ready for copulation by adopting the submissive posture and vibrating her primaries.
Distribution: Africa.
Introduced to Australia.
Status: Not globally threatened. Frequent and abundent throughout most of its range. Their numbers and range have diminished in W and N Africa. Most N African populations are included on the CITES 1 list. The range of the wild population in S Africa is reduced to the NW of their former range, elsewhere there are only feral birds.
The main damage to the populations was caused by the plume trade during the 19th centry and hunting/egg-collecting in the 20th centry. The main threat now is habitat loss. Ostriches breed well in captivity and are kept both on farms and in zoos. There is a feral population in Australia now, derived from a farm population.
Daily Rhythm: The daily activity of Ostriches begins shortly before sunrise and ends soon after sunset, but it does vary depending on the avalibility of food. When food is scarce they must spend a lot more time searching for it, and this may involve travelling great distances. They are most active during the first and last hours of the day, when they heat is less, although they are quite capable of tolerating extreme heats and have been seen stepping out in the midday sun.
At night the roost a regular communal sites, preferably with a favourable wind, in case danger approaches. At such roost sites individulas of the group are always within sight and hearing of one another, but the distances they choose from one another vary. They squat with their necks raised through most of the night, although the eyes are closed. They occasionally go into a deeper sleep, in which they rest their head and neck along the side of the body or streached out in front of themselves, this kind of sleep is always limited to short intervals.
Voice: Ostriches make a series of different sounds including; whistles, snorts, gutteral noises and booming calls. They also make non-vocal sounds such as bill-snapping and stomach rumbling.
Among the most typical sounds made by adults are the males territorial booms, which are used to proclaim territory and during displays. The call consists of a "boo boo booooh hoo" repeated several times at short intervals, it sounds rather like a lions roar, but with out the final growl. At night, booming can be triggered by the presence of a predator or by unusual sounds, such as a storm.
Males also frequently emit a soft "booh" or "twoo", which they normally use in disputes to accompany a threat, attack or retreat. Young birds make several diferent noises, which reflect their mood in a particualr moment, Before hatching they make melodious contact calls, which are answered by their parents.
Enemies: When cornered or in fear of being out run, ostriches drop to the ground and lye with their neck and head streached out in front of them on the ground. This possition is also adopted by the incubating bird.
To avoid becoming prey ostriches often associate with large hoofed animals, such as wildebeest and zebra, these animals are on the look out for much the same predators as the ostrich is.
Ostrich eggs are often taken from their nest by jackals, hyenas or Egyptian vultures.
Prey: Grasses, seeds(Acacia, fig and aloe), roots, leaves, succulent plants are important, some insects (locusts) and small vertebrates (lizards and small tortoises).
Food and Feeding: Omniverous but mostly herbiverous. They eat whatever is most available in each season.
As food is swallowed, it is collected in the crop until a mass has accumulated, then it slides slowly down the the throat, where it can be seen clearly streaching the skin. Many components of an ostriches diet are unpalatable to other animals, and to deal with such tough items, the ostrich has formidable intestines thata re 14 m long, this allows them to get the most out of what they eat. They swallow pebbles and sand to help them break down food in their gizzards and they have a tendancy to pick up small, bright objects.
When searching for food they peck at the floor with great presision at whatever item they have selected. Most of what they browse is within half a meter of the ground, but occasionally they browse at head height.
While they are foraging they have their heads low much of the time and concealed by vegetation. This means that they cannot watch out for predators and they are liable to be attacked. To avoid such attacks ostriches developed two strategies; first, they look up and scan their surroundings at irregular intervals, so that the stalking predators cannot predict when they will next take a look around. Secondly; they stick together in groups so that there is always likly to be at least one pair of eyes on the look out and each individual has less chance of being choosen as the prey. Individuals feeding in a group are known to concentrate more on feeding and do look up much less.
Ostriches do not actually need to drink and most of their water is obtained from succulent plants, these become particualrly important in desert areas.
Grouping: GRoups outside the breeding season tend to be small with 2-5 birds or even solitary animals wandering about. In some areas however they form groups with up to 100 birds, from which members come and go as the please. During the breeding season strict groups are formed, with a pair and sometimes several other females, making a harem. Each group has a pecking order with dominat adult males and females, which are copied in their activities by the other members of the group, with the result that all of the birds tend to sand-bathe or preen at the same time. There are frequent social interactions between individuals, and they sometimes develope into short fights, though these are mostly restricted to disputes bout social rank, or between individuals of the same sex during pair formation. Confrontations are usually settled by means of threatening noises, or by one of the contestants performing a display posture that involves the head being held high, with its neck puffed out and its wing-tips being raised skyward. The threatened bird either flees or adopts the submissive posture, with the head held low, the neck kincked in a U-shape and the wings and tail pointing downwards. Sometimes when the submissive bird flees the dominant bird will persue it and peck and kick its rival.
Breeding: The breeding season varies depending on when it rains. In wetter areas they tend to breed in the dry season, between Juna and October. In arid zones they breed more irregularly, usually taking advantage of the greater availabilty of food after the rains. So in some areas they can breed at any time of the year.
The breeding strategy varies also. Where food is scarce pairs tend to become monogamous, whereas typically they form breeding groups, where the structure of the group becomes quite complex. They consist of a territorial male, the main female and several secondary females. The main female (or major hen) mates with the territorial male, sometimes for several years running and they share the tasks of incubation and subsequent young care. The minor hens mate with several males and lay eggs in several different nests, but do not normally incubate. There are also roving adult males, which mate with adult females, but have no territory or nest. This social structure is complememnted by the number of females, which outnumbers the male population.
On the approach of an individual onto a male territory, he will set off towards it in a dominat posture. If the bird is a male he will expel it, if it is a female he approaches until he is fairly close and then he suddenly flops down on the ground, opens his wings and begins to shake each wing alternately and move his tail up and down. Meanwhile, his head and neck sway from side to side beating against his flanks. After a while he gets up and walk to the female, with his wings open and his neck puffed out, stamping as he goes. Now, depending on her attitude, he either sits agian and repeats the display or he goes to mount her. Females show that they are ready for copulation by adopting the submissive posture and vibrating her primaries.
During copulation the male grunts and groans, repeating his rhytmic neck and wing movements, of the courtship. They usually perform this ritual at dusk but sometimes it takes place during the heat of the day.
After mating with the major hen, not a minor hen which will be left alone after mating, the male leads her to one of the several nests he has prepared. The major hen then starts to lay eggs in the chosen nest, she will lay an egg every 2 days for about 2 weeks. Other females will also lay in the nest when the major hen is absent. Females usually visit the nest ot lay in the early afternoon.
Ostriches only hatch about 10% of all the eggs laid each season, this has something to with the large amount of eggs that are discarded by major hens. Large numbers of young birds are killed or die during their first few months also.
Gestation: Incubation lasts 42-46 days with males sitting by night and females by day.
Litter Size: The major hen lays about 5-11, and minor hens lay about 2-5 each.
Young Description: The glossy white eggs are huge, averaging 159 x 131 mm, with a 2 mm thick shell, however despite their great size the are tiny compaired with the females body size. The eggs weight about 1500g.
When the chicks hatch they are covered with a frizzy down of buff brown with some black lines and specks, they also have a reddish cap. The legs and beaks are pink.
Ostrich chick
Juveniles are similar to the females but darker and plainer.
Nest: A shallow depression about 3 meters wide. Males make these with their feet, usually at a site with good visibility in the center of their territory generally.
Young Care: When the hens are laying in the nest they usually leave it between laying, however when the weather is very hot, or predators are about the major hen will remain with the eggs to guard them.
Adult female Ostrich with chicks
When the major hen begins incubation she will 19-25 eggs beneth her, the rest, as there may be as many as 78 eggs, are pushed out of the nest, so that they form a ring around it. Her own eggs get the most benefit from her incubation time, they are positioned in the center of the nest. She can recognise her own eggs by their size and pore structure. Even though she gives priority to her own eggs there is room in the nest and beneth her for several of the minor hens eggs. The mahor hen performs the task of incubation for the minor hens beacuse their eggs being in her nest means that predators are less likely to take hers. Incubation is shared between the male and female, with the female taking daytime hours and males taking the nightime hours. After about 6 weeks the eggs all hatch simultaneously and it seems that the chicks are stimulated to break open the shell by vocalizations of the mother and also of the other chicks.
Within the chicks first three days of hatching they leave the nest, in the company of their parents. The adults look after their young aheltering them under their wings from sun and rain. When predators threaten the adults perform a distraction display, where the birds rush towards the predator and then flops to the ground, waggling its wings and inflating its neck, trying to give the impression that it is injured perhaps. In the meantime the young birds flee into cover, normally accompanied by the female, or they scatter and flop to the ground, where they are hard to spot.
When two family groups come into contact, the parents dispute the guardianship of both clutches. They usually persue one another in short chases and the victor of this trial will leave with both set of young. In this way groups of 100-300 chicks may be formed, as many as 380 have been recorded, the chicks in such groups may have various ages and may come from diferent areas. These large groups are less vulnerable to predators than small groups.
After 3 months they start to gain their juvenile plumage, which is steadily replaced by adult-like pluamge during their second year. At 4-5 months they are about half the size of an adult and by 1 year they are as tal as adults but they do not achive adult weight until about 18 months.
Some adults stay with their young until the next breeding season, about 9 months, though they may remain together for 12 months, after which the immature birds will move about in their own flocks of mixed ages.
Sexual Maturity: About 3-4 years.
Longevity: 30-40 years. They have lived for up to 50 years in captivity.
Geographical Variations:
Struthio camelus camelus
Distribution: West and South Sahara, Sahel.
Description: Male coat: Skin and beak pink and eyes blue. Plumage black with white 'flight' and tail feathers.
Struthio camelus molybdophanes
Distribution: Somalia to Kenya.
Description: Male coat: Blue-grey skin with some pink shading on legs and beak pink. Feathers black brown with white 'flight' and tail feathers. Eyes brown.
Struthio camelus massaicus
Distribution: South Kenya to Tanzania.
Description: Male coat: Skin pink and beak pink. Eyes brown and feathers black with white neck ring, 'flight' and tail feathers.
Female coat: Dusty brown, skin light grey-brown with similar beak and brown eyes.
Struthio camelus australis
Distribution: South Africa. Now introduced to South Australia.
Description: Male coat: Skin grey-blue with pink beak and brown eyes. The feathers are black brown with white tail and 'flight'f feathers, often orange stained with sand.
Females coat: Skin greyish, beak grey with pink gape. The plumage is darkish brown with grey 'flight' feathers.
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