Ostrich

The common ostrich is a flightless bird native to parts of Africa and is the largest living bird. Males stand 2.1 to 2.75 m tall and weigh 100 to 130 kg, with mostly black feathers and white wing and tail plumes, while females are greyish-brown and white. It lives in nomadic groups of 5 to 50 birds and eats mainly plants, along with invertebrates and small reptiles, swallowing pebbles to grind food in its gizzard because it has no teeth. When threatened it hides flat against the ground or runs, and if cornered it can deliver a powerful forward kick. Territorial males fight for a harem of two to seven females.

About the ostrich

The common ostrich is a flightless bird native to parts of Africa and, historically, Arabia, and it's the largest living species of bird on Earth. It's one of two living ostrich species — the other is the Somali ostrich, recognized as its own species by BirdLife International since 2014 — and both are the only living members of the genus Struthio in the ratite group of flightless birds. The order Struthioniformes once included all the ratites, such as kiwis, emus, rheas, and cassowaries, but genetic analysis has since shown that grouping wasn't accurate, and today ostriches stand alone in their order, as the sister group to all other members of the Palaeognathae.

An ostrich is unmistakable: a long neck and long legs on a huge frame, capable of running for extended periods at 55 km/h (34 mph) with bursts up to about 70 km/h (43 mph) — the fastest land speed of any bipedal animal. Males stand 2.1 to 2.75 m (6 ft 11 in to 9 ft) tall and weigh 100 to 130 kg (220 to 290 lb), with some exceptional individuals of the nominate subspecies reaching 156.8 kg (346 lb); females are somewhat smaller, standing 1.75 to 1.9 m (5 ft 9 in to 6 ft 3 in) tall and weighing 90 to 120 kg (200 to 260 lb). Adult males are mostly black with white primary feathers and a white tail, while females and young males are greyish-brown and white. The head and neck are nearly bare, covered only by a thin layer of down, and the eyes — the largest of any land vertebrate at 50 mm (2.0 in) across — sit shaded from direct sun, helping the bird spot predators from a distance. The legs are strong, unfeathered, and scaled, red in males and black in females, and the feet have just two toes each, an adaptation that helps with running. The species also lays the largest eggs of any living bird.

Behavior and diet

Ostriches spend the winter months mostly in pairs or alone; only 16 percent of recorded sightings involve more than two birds together. During the breeding season, and sometimes during extended dry spells, they gather into nomadic groups of five to 100 birds led by a dominant hen, often traveling alongside other grazing animals such as zebras or antelope. They're diurnal but sometimes active on moonlit nights, most alert early and late in the day. A male's territory covers roughly 2 to 20 km² (0.77–7.72 sq mi). Their eyesight and hearing let them detect predators like lions from a long way off; when threatened, they typically run, but if cornered they can deliver a forward kick powerful enough to cause serious injury or death, generating up to 225 kgf (2,210 N) of force. When hiding, an ostrich will lay its head and neck flat against the ground, making it look like a mound of earth from a distance.

An ostrich's diet is mostly plant matter — seeds, shrubs, grass, fruit, and flowers — with occasional insects, small mammals, small reptiles, and animal remains left behind by predators. Lacking teeth, it swallows pebbles that serve as gastroliths, grinding food down inside the gizzard, which can hold as much as 1,300 g (46 oz), up to 45% of that sand and pebbles. Ostriches can go days without drinking, relying on metabolic water and moisture from the plants they eat, though they'll bathe and drink freely when water is available and can survive losing up to 25% of their body weight to dehydration.

Ostriches reach sexual maturity between two and four years old, with females maturing about six months ahead of males. The mating season runs from March or April to sometime before September. Territorial males boom to defend their ground and a harem of two to seven hens, mating with several females but pair-bonding with only one "major" female, in an elaborate courtship of wing-beating and ground-poking before the pair mates. All the hens in a male's harem lay their eggs in one shared nest, a pit 30 to 60 cm (12 to 24 in) deep and 3 m (9.8 ft) wide scraped into the ground; the dominant female lays first and later discards extra eggs from weaker females, usually leaving about 20, which she can distinguish from the rest. Ostrich eggs are the largest of any bird's, at around 15 cm (5.9 in) long, 13 cm (5.1 in) wide, and 1.4 kg (3.1 lb) — over 20 times the weight of a chicken egg, though relative to the adult bird's size, they're actually the smallest eggs of any bird species. Incubation is split between the sexes, females by day and males by night.

Range and habitat

Common ostriches historically ranged across Africa north and south of the Sahara, through East Africa and the savanna belt south of the rainforest zone, and into much of Asia Minor. Today they're native to the savannas and Sahel of Africa on both sides of the equatorial forest zone, with populations in southwest Africa extending into semi-desert and true desert. Arabian ostriches once lived across the Near and Middle East but were hunted to extinction by the mid-20th century, and later attempts to reintroduce the species to Israel failed. Farmed ostriches have also established small feral populations outside Africa, notably in the Australian outback.

Conservation status

The common ostrich is listed as Least Concern on the IUCN Red List, in a 2018 assessment by BirdLife International. The rating rests on its enormous range, about 9.8 million km² (3.8 million sq mi), not on healthy numbers: the wild population has declined drastically over the last 200 years, and most surviving birds live in reserves or on farms.

Some populations are already gone. The Arabian ostrich, one of its subspecies, became extinct around 1966 after hunting, and attempts to reintroduce the common ostrich into Israel have failed. North African populations are listed on CITES Appendix I, which bans commercial international trade.

The bird is also farmed widely around the world for its feathers, its skin for leather and its lean meat.