Australian parrots and how they have adjusted to changing habitats

A Parrots are found across the tropics and in all southern hemisphere continents except Antarctica, but nowhere do they display such a richness of diversity and form as in Australia. One-sixth of the world's 345 parrot species are found there, and Australia has long been renowned for the number and variety of its parrots.

B In the 16th century, the German cartographer Mercator made a world map that included a place, somewhere near present-day Australia, that he named Terra Psittacorum – the Land of Parrots – and the first European settlers in Australia often referred to the country as Parrot Land. In 1865, the celebrated British naturalist and wildlife artist John Gould said: "No group of birds gives Australia so tropical and benign an air as the numerous species of this great family by which it is tenanted."

C Parrots are descendants of an ancient line. Due to their great diversity, and since most species inhabit Africa, Australia, and South America, it seems almost certain that parrots originated millions of years ago on the ancient southern continent of Gondwana, before it broke up into the separate southern hemisphere continents we know today. Much of Gondwana comprised vast rainforests intersected by huge slow-flowing rivers and expansive lakes, but by eight million years ago, great changes were underway. The centre of the continent of Australia had begun to dry out, and the rainforests that once covered it gradually contracted to the continental margins, where, to a limited extent, they still exist today.

D The creatures that remained in those shrinking rainforests had to adapt to the drier conditions or face extinction. Reacting to these desperate circumstances, the parrot family, typically found in jungles in other parts of the world, has populated some of Australia's harshest environments. The parrots spread from ancestral forests through eucalypt woodlands to colonise the central deserts of Australia, and as a consequence they diversified into a wide range of species with adaptations that reflect the many changes animals and plants had to make to survive in these areas.

E These evolutionary pressures helped mould keratin, the substance from which beaks are made, into a range of tools capable of gathering the new food types favoured by various species of parrot. The size of a parrot's short, blunt beak and the length of that beak's curved upper section are related to the type of food each species eats. Some have comparatively long beaks that are perfect for extracting seeds from fruit; others have broader and stronger beaks that are designed for cracking hard seeds.

F Differently shaped beaks are not the only adaptations that have been made during the developing relationship between parrots and their food plants. Like all of Australia's many honey-eating birds, the rainbow-coloured lorikeets and the flowers on which they feed have long co-evolved, with features such as the shape and colour of the flowers adapted to the birds' particular needs. For example, red is the most attractive colour to birds, and thus flowers which depend on birds for pollination are more often red, and lorikeets' tongues have bristles which help them to collect as much pollen as possible.

G Today, most of Australia's parrots inhabit woodland and open forest, and their numbers decline towards both deserts and wetter areas. The majority are nomadic to some degree, moving around to take advantage of feeding and breeding places. Two of the dry country parrots, the pink and grey galah and the pink, white, and yellow corella, have expanded their ranges in recent years. They are among the species that have adapted well to the changes brought about by European settlement: forest felling created grasslands where galahs and corellas thrive.

H But other parrot species did not fare so well when their environments were altered. The clearing of large areas of rainforest is probably responsible for the disappearance of the double-eyed fig parrot, and numbers of ground parrots declined when a great part of their habitat was destroyed by the draining of coastal swamps. Even some parrot species that benefited from forest clearing at first are now confronted by a shortage of nesting sites due to further man-made changes.

I New conditions also sometimes favour an incoming species over one that originally inhabited the area. For example, after farmers cleared large areas of forest on Kangaroo Island off the coast of South Australia, the island was colonised by galahs. They were soon going down holes and destroying black cockatoo eggs in order to take the hole for their own use. Their success precipitated a partial collapse in the black cockatoo population when the latter lost the struggle for scarce nesting hollows.

J There may be no final answer to ensuring an equitable balance between parrot species. Nest box programmes help ease the shortage of nesting sites in some places, but there are not enough, they are expensive, and they are not an adequate substitute for large, old trees, such as the habitat they represent and the nectar, pollen, and seeds they provide. Competition between parrots for nest sites is a result of the changes we humans have made to the Earth. We are the most widespread and dangerous competitors that parrots have ever had to face, but we also have the knowledge and skill to maintain the wonderfully rich diversity of Australia's parrots. All we need is the will to do so.

The Bovids

A The family of mammals called bovids belongs to the Artiodactyl class, which also includes giraffes. Bovids are a highly diverse group consisting of 137 species, some of which are man’s most important domestic animals.

B Bovids are well represented in most parts of Eurasia and Southeast Asian islands, but they are by far the most numerous and diverse in the latter. Some species of bovid are solitary, but others live in large groups with complex social structures. Although bovids have adapted to a wide range of habitats, from arctic tundra to deep tropical forest, the majority of species favour open grassland, scrub, or desert. This diversity of habitat is also matched by great diversity in size and form: at one extreme is the royal antelope of West Africa, which stands a mere 25 cm at the shoulder; at the other, the massively built bison of North America and Europe, growing to a shoulder height of 2.2 m.

C Despite differences in size and appearance, bovids are united by the possession of certain common features. All species are ruminants, which means that they retain undigested food in their stomachs and regurgitate it as necessary. Bovids are almost exclusively herbivorous: plant-eating. Incisors: front teeth herbivorous.

D Typically, their teeth are highly modified for browsing and grazing: grass or foliage is cropped with the upper lip and lower incisors (the upper incisors are usually absent), and then ground down by the cheek teeth. As well as having cloven, or split, hooves, the males of all bovid species and the females of most carry horns. Bovid horns have bony cores covered in a sheath of horny material that is constantly renewed from within; they are unbranched and never shed. They vary in shape and size: the relatively simple horns of a large Indian buffalo may measure around 4 m from tip to tip along the outer curve, while the various gazelles have horns with a variety of elegant curves.

E Five groups, or sub-families, may be distinguished: Bovinae, Antelope, Caprinae, Cephalophinae, and Antilocapridae. The sub-family Bovinae comprises most of the larger bovids, including the African bongo, and nilgae, eland, bison, and cattle. Unlike most other bovids, they are all non-territorial. The ancestors of the various species of domestic cattle – banteng, gaur, yak, and water buffalo – are generally rare and endangered in the wild, while the auroch (the ancestor of the domestic cattle of Europe) is extinct.

F The term ‘antelope’ is not a very precise zoological name – it is used to loosely describe a number of bovids that have followed different lines of development. Antelopes are typically long-legged, fast-running species, often with long horns that may be laid along the back when the animal is in full flight. There are two main sub-groups of antelope: Hippotraginae, which includes the oryx and the addax, and Antilopinae, which generally contains slighter and more graceful animals such as gazelle and the springbok. Antelopes are mainly grassland species, but many have adapted to flooded grasslands: pukus, waterbucks, and lechwes are all good at swimming, usually feeding in deep water, while the sitatunga has long, splayed hooves that enable it to walk freely on swampy ground.

G The sub-family Caprinae includes the sheep and the goat, together with various relatives such as the goral and the tahr. Most are woolly or have long hair. Several species, such as wild goats, chamois, and ibex, are agile cliff- and mountain-dwellers. Tolerance of extreme conditions is most marked in this group: Barbary and bighorn sheep have adapted to arid deserts, while Rocky Mountain sheep survive high up in mountains and musk oxen in arctic tundra.

H The duiker of Africa belongs to the Cephalophinae sub-family. It is generally small and solitary, often living in thick forest. Although mainly feeding on grass and leaves, some duikers – unlike most other bovids – are believed to eat insects and feed on dead animal carcasses, and even to kill small animals.

I The pronghorn is the sole survivor of a New World sub-family of herbivorous ruminants, the Antilocapridae in North America. It is similar in appearance and habits to the Old-World antelope. Although greatly reduced in numbers since the arrival of Europeans and the subsequent enclosure of grasslands, the pronghorn is still found in considerable numbers throughout North America, from Washington State to Mexico. When alarmed by the approach of wolves or other predators, hairs on the pronghorn’s rump stand erect, so showing and emphasizing the white patch there. At this signal, the whole herd gallops off at a speed of over 60 km per hour.