Ratite

Ratite

Several groups of flightless birds are often grouped together as ratites. Their most striking common characteristic is the lack of a large keel on the sternum (hence ratites from the Latin rata, a raft, as opposed to the birds with a keeled sternum, the craniates from czarina, a keel). However, with the evolution of lightlessness, the need for large flight muscles and they’re attach mint areas becomes unnecessary. Hence this loss of the keel would be what one would expect with the development of lightlessness and it is not clear whether all these groups are really closely related or not further fossil finds may help to elucidate this problem.

The ostrich is famous for being the largest living bird and for being flightless. Despite the allegation of legend and unflattering popular sayings, no ostrich has yet been observed to bury its head in the sand. Ostriches are widely distributed on the flatter open low-rainfall areas of Africa, in four clearly recognizable subspecies. The North. African ostrich with pink neck inhabits the southern Sahara the blue necked Somali ostrich occupies the Horn of Africa adjacent is the pink-necked Masaiostrich which lives in East Africa and south of the Zambezi is the blue-necked South Afro-can ostrich.

The ostrich is enormous. Its feathers are soft and without barbs. The jet-black plumage of the male makes him highly con-spacious at long distances by day, and his long white outer “flight” feathers (pry-marries) contrast strikingly. The brownish color of females and juveniles renders them well camouflaged (newly hatched chicks are fawn with dark brown spots and a conceal-in hedgehog-like cape of bristly down on the back). The neck is long and highly mobile, the head small, the gape of the unspecialized beak wide, and the eyes enormous.

Vision is acute. The thighs are bare, the legs are long and powerful, and there are only two toes on each foot. The bird can kick forwards powerfully and can run at about 50 km/h (3 mph). Ostriches are tireless walkers. Thanks to their large stride, long neck, and precise peck ostriches are highly efficient selective gatherers of the sparsely dispersed high-quality food items in their habitat. They take a very wide variety of nutritious shoots, leaves, flowers, and seeds. The takings of many pecks are amassed in the gullet and then pass slowly down the neck as a large ball (bolus) which stretches the neck skin as it descends. Ostriches feeding with their beaks down among vegetation are vulnerable to predators (lions, and occasionally leopards and cheetahs) they periodically raise their heads to scan the landscape for danger.

Breeding seasons vary with locality, burin East African ostriches mainly nest in theory season. A male makes a number of shall-low scrapes in his territory. A female (the “major” hen), with whom he has a loose pair bond, selects one of these scrapes. She lays, on alternate days, up to a dozen eggs. Up to six or more other females (”minor “hens) also lie in the nest but play no other role there. The major hen and the cock share equally, for increasing periods, in first guarding and later incubating the clutch the female by day, the male by night unguarded nests are conspicuous from above, and vulnerable to predation by Egyptian vultures which throw stones at the huge eggs to break through their shells(2mm thick). Even guarded nests are at risk from hyenas and possibly jackals. Fewer than I o percent of the nests started to survive the roughly three-week laying period and six-week incubation period.

Ostrich chicks are well-developed (precocious). They are accompanied by both males and females who try to protect them from the many threatening raptors and ground predators. Chicks from several different nests usually combine into single large groups, escorted by one or two adults. Only about 1 5 percent of chicks hatched survive to one year old when they will be full height. Females can breed at two. Males start to acquire adult plumage when two, and cambered at three or four. They can probably live to be over 40.

Males defend their territories in the breed-in season by patrolling and by displaying to and chasing out intruders, and by boom-in.  Aggressive dies-plays consist of repeated flicking of wings and postures with both wings raised. Breed-in males display dramatically yet absurdly to females by squatting and waving their huge spread wings alternately. Females soli-cit by lowering the head and both wings and quivering the latter. Groups of birds are usually small and not cohesive. Adult ostriches spend much of their time alone.

In few other bird species do some individuals willingly look after the eggs of other individuals, since natural selection usually disfavors such apparently altruistic behavior? The large size of ostriches and the vulnerability of their nests to predation are probably the factors allowing it in this species. An ostrich egg is not only the largest bird’s egg but also the smallest in relation to the size of the bird. As a result, an ostrich can cover a great many of them, either more than a female can lie or more than is worthwhile for her laying herself (with the delays and risks involved in doing so).

The skewed serration among breeding adults, with about 1.4 females per male, and the high rate of nest destruction by predators both mean that there are many hens without their own nests to lie in. It obviously benefits them today somewhere. The major hen benefits from the presence of extra eggs in her nest, because her own is protected by a dilution effect against small-scale predators (i.e. heron eggs. probably a dozen among about 20. are less likely to be damaged). If, as frequently happens. More eggs are laid inhere nest than she can cover. At the start of incubation, she rolls away the surplus into an outer ring outside the nest, where they are not incubated and are doomed. As she’s able to discriminate among the many eggs in the nest, she ensures that the eggs she rolls out are not hers. It is an astonishing feat of recognition, for ostrich eggs do notary much in appearance.

High levels of predator density or human activity make nests unlikely to survive. Delinquent hunting drove the once-abundant Arabian ostrich to extinction earlier this century. Ostrich populations today are decreasing with human intrusion into their habitat, but the species is not severely threatened. Ostrich feathers have long been used by African peoples for adornment and by Europeans since Roman times. An ostrich feather, being symmetrical, was the symbol of justice in ancient Egypt, where also ostrich brains were a delicacy. Pieces of eggshells are used in necklaces and waistbands. More mundanely, the Hottentots used empty eggshells as water containers. Rheas are large flightless birds frequently called the South American ostrich. Anatomically and taxonomically rheas are quite distinct from the ostrich. Rheas may stand up to 1.5m (5ft) tall, but most never weigh more than 40 kg (88 lb). Ostriches may reach over 2m (6.5ft) in height and may weigh up to 200kg (Apart from the size the most obvious difference occurs in the feet: ostriches have only two enlarged toes, while rheas possess three toes, as do most other birds.

The Gray or Common rhea was once a common inhabitant of the grassland regions from central and coastal Brazil down to the pampas of Argentina. This species contains three distinguishable subspecies. The small-est., from Brazil, weighs only 2 kg (441b) while the larger Argentinean subspecies may weigh up to 4 kg (881b). Darwin’s or lesser rhea is also divided into three subspecies. Darwin’s rhea is found on the semi-desert grass and scrublands of Patagonia and on the high-altitude grasslands of the Andes from Argentina and Chile, north through Bolivia into Peru.

Both rhea species tend to congregate in flocks for the winter months and divide into smaller flocks for the breeding season, when males may become solitary for incubating (see box). Rhea chicks are raised by males. They feed largely on insects for their first few days, but gradually follow the example of their fathers and begin feeding on vegetation. Male rheas defend their chicks from all intruders, including other rheas males with chicks are often seen driving females away from the chicks. Male rheas with chicks have been known to attack small planes and regularly charge gauchos (South American cowboys) on horseback.

The threat of a rhea charge, which could cause a horse to shy and bolt, is one reason why most gauchos are accompanied by dogs, so they can if necessary scare off or divert the attack of a male rhea. By the end of the summer males, chicks and females gather into large flocks for the winter. In spring, when males become solitary and females form small groups, the yearlings usually remain as a flock, which lasts until they are nearly two years old and ready to breed. Adult rheas are largely vegetarian and feed on a great variety of plants. The Gray rhea eats some grass but strongly prefers broad-leaved plants and frequently eats even obnoxious weeds, such as thistles. Clover seems to be a favorite. The Darwin’s rhea. Found generally in a drier or harsher environment, will eat almost anything green, but prefers broad-leaved plants. All rheas eat insects and small animals, such as reptiles, when they have the opportunity.

When rheas have come into contact with humans they have usually been persecuted. They have been hunted for years and are one of the main animals caught with the famous bolas. Rhea feathers are used to make feather dusters throughout South America. Rheas and their eggs are regularly eaten by local people or are killed and used for dog food. Rheas can coexist with cattle and sheep ranching even though many ran-cheers accuse the rhea of competing with cat-tale or sheep. In actuality, competition is probably minimal because rheas eat a lot of unwanted plant species as well as vast numbers of insects. However, once the land is put to agricultural use the rheas are eliminated because they will eat almost any agricultural crop. They now thrive only in remote areas, away from man or where they are protected.

The decline of rhea populations has prompted the Convention for International Trade in Endangered Species to list both the rhea species and all subspecies as either endangered or threatened. Thereby requiring permits for their export or import. In recent times adult rheas have had few natural enemies other than a man. The Gray rhea on the pampas of Argentina and in the savanna and reverie grasslands has a virtue-ally limitless food supply. The large predatory cats like the jaguar and Mountain lion do not regularly frequent the vast pampas grasslands and smaller predators cannot readily kill an adult rhea. However, rhea chicks are quite vulnerable to a number of predators, including an array of mammals and birds of prey like the caracara. While protected by the male small chicks are safe however, small chicks separated from the male, particularly after a sudden thunderstorm, are easily taken by predators. Even the small kestrel-sized chi mango canes a successful predator when chicks have become separated from their parent.

In Australia, there is a saying “As stupid as an emu.” Emus, however, have been resident in Australia for at least 8o million years, ever since it broke away from the great prehistoric Antarctic continent, Gondwanaland, and began drifting north. In fact, the nomadic emu is well adapted to survive in the harsh Australian environment. Studies show that the way of life of the bird nicely matches the conditions with which it has to come to terms.

Until the late 18th century there were several species and subspecies of the emu. The Dwarf emus of King Island (Bass Strait) and Kangaroo Island (South Australia) as well as the Tasmanian subspecies were exterminated soon after Europeans settled in Australia. On mainland Australia the emu remains widespread, taking its place as one of Australia’s large native herbivores. It live-in eucalypt forests, woodland, male, heathland, desert scrublands, and sandplains. In desert areas it is rare, being found there only after heavy rains have induced the growth of an array of herbs and grasses and caused shrubs to fruit heavily. The emu also lives close to Australia’s big cities but is no longer found where native vegetation has been cleared to provide agricultural land. Whatever the habitat, however, the emu must have access to fresh water, usually every day.

Emus are large shaggy birds: their loose double feathers, in which the after shaft (the secondary feather that branches from the base of the main feather) is the same length as the feather, hang limply from their bodies. Their necks and legs are long but their wings are tiny, reduced to less than20CITI (8in). After molting the birds are dark, but as sunlight fades the pigments (melanin) that gave the feathers their brown color, so the birds become paler. Their long legs enable them to walk long distances at a steady 7km/h (4mph) or to flee from the danger at 48km/h (Emu shave three toes (differing in this from the ostrich which has only two). Emu chicks are striped longitudinally with black, brown, and cream, so they blend easily into the long grass and dense shrubbery.

The emu prefers and seeks a very nutritious diet. It takes the parts of plantain in which nutrients are concentrated: seeds, fruits, flowers, and young shoots. It will also eat insects and small vertebrates when they are easily available, but in the wild, it will not treat dry grass or mature leaves even if they are all that is available.

Grind up its food it also often eats charcoal. Its rich diet enables it to grow fast and reproduce rapidly but at a price. Because such rich foods are not always available in the same place throughout the year emus must move to remain in contact with their foods. In arid Australia, the exhaustion of afoot supply in one place often means moving hundreds of kilometers to find another source of food.

Firstly, when foodies are abundant and lay down large stores of fat it is able to use these while looking for more food, so birds normally weighing 45kg(T o51b) can keep moving at body weights sallow as 2okg (441b). Secondly, emus are only forced to stay in one place when the males sit on eggs. At other times they can move without limitation, admittedly at a sallow pace when with small chicks. During incubation the male does not eat, drink or defecate, so he is then independent of the estate of the local food supply. Emus pair in December and January, two birds defending a territory of about 30 sq km while the female lays her clutch of 9-20 eggs in April, May, and June. A few stay to defend the male in the nest, using their characteristic loud booming call. Males are very aggressive when the chicks hatch, after 56 days they drive the female away and attack approaching humans. 

the parent’s young bond breaks down and the male may then remote for the next season’s nesting.
Emus have probably benefitted from man’s activities in inland Australia because the establishment of watering points for cattle and sheep has provided permanent water where there was none before, and so much of Australia is unoccupied or used aspen rangeland that the emu is in no danger of extinction. Many people have seen their footprints, their feces, or even heard them call, but glimpses of the birds are rare. The largest land animals in New Guinea have kept their secrets well: we still have only the barest outline of their life history.

The three species of cassowaries live in New Guinea. The largest, the Southern cassowary, also inhabits Cape York. Ceram Andiron Island. The One-wattle cassowary, only slightly smaller than the Southern, is confined to New Guinea. The murk or Ben-net’s cassowary, little more than 17 M (4oin) tall lives in New Guinea, New Britain AndYapen Island.

All three species have sleek, drooping, brown, or black plumage. Their wing quills are enlarged, spike-like structures, used for infighting and defense. The three toes on their feet are also effective weapons: the kick-oaf cassowary has disemboweled many adversaries. In all species the legs and neck are long, and the head is adorned with a hornycasque (higher in the female than the male). The neck is ornamented with colorful bare skin and small fleshy flaps (wattles). The sexes are alike. When chicks the plumages are striped brown, black and white, changing to a uniform brown for the first year of life. The glossy black adult plumage begins to grow during the second year and is fully developed at four years. The casqued on the head is often thought to be used by the birds to push through the thick jungle. Recently captive bird was seen using it to turn over soil as they sought food. Perhaps wild cassowaries use the casqued to turn over the lit-tar, seeking small animals, fallen fruit, and Fungi.

Cassowaries feed mainly on the fruit of forest trees, which they eat whole. As the fruit of these trees grows high in the canopy and the cassowaries cannot fly they are dependent on finding fallen fruit. Throughout the year, only forests with a good diversity of tree species will sustain the population of cassowaries. Many forests used for timber production no longer retain their primitive diversity, so in a slow and subtle way, they are becoming less capable of supporting cassowaries. The more, unlike the other two species which live only in the jungle, also has sparse populations in many mountainous parts of New Guinea. In these places, it seems to feed on the fruits of those shrubs and healthy plants from which it can take direct. All species will also feed on insects, invertebrates, small vertebrates, and some fungi.

Cassowaries are solitary animals, forming pairs in the breeding season but at other times found alone. The male incubates the 4-8 eggs in a nest on the forest floor. He accompanies the chicks for about a year before returning to his solitary life. The bird’s most commonly heard call is a deep “chug,” but during courtship in the Southern cassowary, the male approaches the female giving a low “boo-boo-boo” call, circling her and causing his throat to swell.

Conserving Kiwis

In New, Zealand kiwis have suffered considerably since European settlement began 5o years ago. Large areas were cleared forearming and, in addition, the European settlers introduced mammal predators such as cats and stoats. The Great spotted kiwi and the Brown kiwi on the South Island and the Brown kiwi on Stewart Island are still widespread and appear to be able to hold their own. In the North Island, however, the Brown kiwi is under threat from land clearance over much of its range. Dedicated catching teams attempt to remove the kiwis before the land is cleared but cannot cope with the large areas involved. Fortunately, the kiwi has adapted to some man-modified habitats and also lives on in the few large forest reserves within its range.

The Little spotted kiwi has fared the worst and is endangered. The species would be all and tremble. Most contacts between wild cassowaries observed outside the breeding season led to fights. It is assumed from their distribution that individuals, at least of the Southern cassowary, are territorial. Cassowaries need large areas of forest in which to live.  Breeding (in winter) coincided with the period when the maximum amount of fruit was available in the forest. The survival of the cassowaries may therefore depend upon the survival of diverse forests whereat is possible for them to obtain food throughout the year. Kiwis have taken lightlessness to the extreme. Their tiny vestigial wings are buried in their feathers and their tail has died-appeared externally. The kiwi lays an egg that is one-quarter of her weight and, unlike most other birds, kiwis use their sense of smell rather than their sight to investigate their surroundings.

Kiwis remain fairly widely distributed in New Zealand but have disappeared from large areas, not only where the original native forest has been removed but also from some areas still forested. The North Island subspecies of Brown kiwi has even colonized some exotic pine forests and farmland with mixed scrub and pasture. The South Island brown kiwi and the Great spotted kiwi are confined to the remoter forests and mountains of the western side of the South Island. The Stewart Island brown kiwi occurs in forest, scrub, and tussock grassland, and is the only kiwi active in daylight. The Little spotted kiwi, once widespread on both the North and South Islands, is now known on only three offshore islands.

The kiwi is the size of a domestic hen’s butts body is more elongated and has stouter, more powerful legs. Its long, curved bill, which has openings for air passages at the tip, is used for probing the ground for food. There is no breastbone (sternum), to which in other birds the flight muscles are attached other bones that are hollow in most birds (so as to reduce weight for flight) are only partly hollow in kiwis. Although their eyes are small for a nocturnal animal, kiwis can see well enough to run at speed through dense undergrowth. Compared with its flightless relatives, the ostrich, rheas, and emus, the kiwi is a small bird and could probably have evolved only in the absence of mammals. The New Zealand archipelago was formed 80-7 of million years ago, before the evolution of efficient land mammals. When mammals appeared there was a sea barrier that prevented them from reaching New Zealand and protected the kiwis, and their ancestors, from their competition and predation. Other flightless birds (the moans) also evolved in New Zealand, but all are now extinct.

The kiwi has invested enormous energy in each large egg rather than in a clutch of many smaller eggs. Its egg is highly nutritious and not only sustains the embryo throughout the long incubation but also provides the newly hatched chick with a yolk sac as a temporary food supply. After an egg has been laid it is believed that the egg is left unattended for several days, but once incubation begins it is the work of the male. There is some doubt as to whether parents feed their chicks certainly, within a week of their birth, the chicks emerge from the nest alone and attempt to feed them.

The kiwi is able to detect food by smell and uses its bill to probe amongst the forest litter, or for thrusting deep into the soil. It picks up food in the tip of its bill and throws it back to its throat in quick jerks. Kiwis are distributed in pairs and use calls to keep in contact in the dense forest and also to maintain territories. At closer range the kiwi again uses its sense of smell rather than sight, as well as its good hearing, to detect other birds. No territory holders are vigorously repelled. Breeding behavior includes loud grunting and snorting as well as wild running and chasing. The kiwi has always been an important bird to New Zealanders. To the Maori, it provided a source of food and feathers for highly valued cloaks.

Today the peculiarity of the kiwi in New Zealand is recognized in that it has been adopted as the unofficial national emblem.

See more: What is a Bird?