Plumage in the context of "House sparrow"

Penguins are a group of flightless, semi-aquatic, sea birds which live almost exclusively in the Southern Hemisphere. Only one species, the Galápagos penguin, lives at, and slightly north of, the equator. Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed on krill, fish, squid and other forms of sea life which they catch with their bills and swallow whole while swimming. A penguin has a spiny tongue and powerful jaws to grip slippery prey.

They spend about half of their lives on land and the other half in the sea. The largest living species is the emperor penguin (Aptenodytes forsteri): on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 30–33 cm (12–13 in) tall and weighs 1.2–1.3 kg (2.6–2.9 lb). Today, larger penguins generally inhabit colder regions, and smaller penguins inhabit regions with temperate or tropical climates. Some prehistoric penguin species were enormous: as tall or heavy as an adult human. There was a great diversity of species in subantarctic regions, and at least one giant species in a region around 2,000 km south of the equator 35 mya, during the Late Eocene, a climate decidedly warmer than today.

Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant birds from other living groups.

Although feathers cover most of the bird's body, they arise only from certain well-defined tracts on the skin. They aid in flight, thermal insulation, and waterproofing. In addition, coloration helps in communication and protection. The study of feathers is called plumology (or plumage science).

Sexual selection is a mechanism of evolution in which members of one sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). These two forms of selection mean that some individuals have greater reproductive success than others within a population, for example because they are more attractive or prefer more attractive partners to produce offspring. Successful males benefit from frequent mating and monopolizing access to one or more fertile females. Females can maximise the return on the energy they invest in reproduction by selecting and mating with the best males.

The concept was first articulated by Charles Darwin who wrote of a "second agency" other than natural selection, in which competition between mate candidates could lead to speciation. The theory was given a mathematical basis by Ronald Fisher in the early 20th century. Sexual selection can lead males to extreme efforts to demonstrate their fitness to be chosen by females, producing sexual dimorphism in secondary sexual characteristics, such as the ornate plumage of birds-of-paradise and peafowl, or the antlers of deer. Depending on the species, these rules can be reversed. This is caused by a positive feedback mechanism known as a Fisherian runaway, where the passing-on of the desire for a trait in one sex is as important as having the trait in the other sex in producing the runaway effect. Although the sexy son hypothesis indicates that females would prefer male offspring, Fisher's principle explains why the sex ratio is most often 1:1. Sexual selection is widely distributed in the animal kingdom, and is also found in plants and fungi.

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into the ocean or coastal waters, but spills may also occur on land. Oil spills can result from the release of crude oil from tankers, offshore platforms, drilling rigs, and wells. They may also involve spills of refined petroleum products, such as gasoline and diesel fuel, as well as their by-products. Additionally, heavier fuels used by large ships, such as bunker fuel, or spills of any oily refuse or waste oil, contribute to such incidents. These spills can have severe environmental and economic consequences.

Oil spills penetrate into the structure of the plumage of birds and the fur of mammals, reducing its insulating ability, and making them more vulnerable to temperature fluctuations and much less buoyant in the water. Cleanup and recovery from an oil spill is difficult and depends upon many factors, including the type of oil spilled, the temperature of the water (affecting evaporation and biodegradation), and the types of shorelines and beaches involved. Spills may take weeks, months or even years to clean up.

The dodo (Raphus cucullatus) is an extinct flightless bird that was endemic to Mauritius, an island east of Madagascar in the Indian Ocean. The dodo's closest relative was the also-extinct and flightless Rodrigues solitaire. The two formed the subtribe Raphina, a clade of extinct flightless birds that are a part of the group that includes pigeons and doves (the family Columbidae). The closest living relative of the dodo is the Nicobar pigeon. A white dodo was once thought to have existed on the nearby island of Réunion, but it is now believed that this assumption was merely confusion based on the also-extinct Réunion ibis and paintings of white dodos.

Subfossil remains show the dodo measured about 62.6–75 centimetres (2.05–2.46 ft) in height and may have weighed 10.6–17.5 kg (23–39 lb) in the wild. The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Since these portraits vary considerably, and since only some of the illustrations are known to have been drawn from live specimens, the dodos' exact appearance in life remains unresolved, and little is known about its behaviour. It has been depicted with brownish-grey plumage, yellow feet, a tuft of tail feathers, a grey, naked head, and a black, yellow, and green beak. It used gizzard stones to help digest its food, which is thought to have included fruits, and its main habitat is believed to have been the woods in the drier coastal areas of Mauritius. One account states its clutch consisted of a single egg. It is presumed that the dodo became flightless because of the ready availability of abundant food sources and a relative absence of predators on Mauritius. Though the dodo has historically been portrayed as being fat and clumsy, it is now thought to have been well-adapted for its ecosystem.

Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly coloured birds in the order Coraciiformes. They have a cosmopolitan distribution: most species live in the tropical regions of Africa, Asia, and Oceania, but they can also be found in Europe and the Americas. They can be found in deep forests near calm ponds and small rivers. The family contains 118 species and is divided into three subfamilies and 19 genera. All kingfishers have large heads, long, sharp, pointed bills, short legs, and stubby tails. Most species have bright plumage with only small differences between the sexes. Most species are tropical in distribution, and a slight majority are found only in forests.

They consume a wide range of prey, usually caught by swooping down from a perch. While kingfishers are usually thought to live near rivers and eat fish, many species live away from water and eat small invertebrates. Like other members of their order, they nest in cavities, usually tunnels dug into the natural or artificial banks in the ground. Some kingfishers nest in arboreal termite nests. A few species, principally insular forms, are threatened with extinction. In Britain, the word "kingfisher" normally refers to the common kingfisher.

The emperor penguin (Aptenodytes forsteri) is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching 100 cm (39 in) in length and weighing from 22 to 45 kg (49 to 99 lb). Feathers of the head and back are black and sharply delineated from the white belly, pale-yellow breast and bright-yellow ear patches.

Like all species of penguin, the emperor is flightless, with a streamlined body, and wings stiffened and flattened into flippers for a marine habitat. Its diet consists primarily of fish, but also includes crustaceans, such as krill, and cephalopods, such as squid. While hunting, the species can remain submerged around 20 minutes, diving to a depth of 535 m (1,755 ft). It has several adaptations to facilitate this, including an unusually structured haemoglobin to allow it to function at low oxygen levels, solid bones to reduce barotrauma, and the ability to reduce its metabolism and shut down non-essential organ functions.

The New World quail are small birds, that despite their similar appearance and habits to the Old World quail, belong to a different family known as the Odontophoridae. In contrast, the Old World quail are in the Phasianidae family, sharing only a remote phylogenetic connection with their New World counterparts through their mutual classification within the Phasianoidea superfamily. The geographical range of the New World quail extends from Canada to southern Brazil, and two species, the California quail and the bobwhite quail, have been successfully introduced to New Zealand. The stone partridge and Nahan's partridge, both found in Africa, seem to belong to the family. Species are found across a variety of habitats from tropical rainforest to deserts, although a few species are capable of surviving at very low temperatures. There are 34 species divided into 10 genera.

The legs of most New World quails are short but powerful, with some species having very thick legs for digging. They lack the spurs of many Old World galliformes. Although they are capable of short bursts of strong flight, New World quails prefer to walk, and run from danger (or hide), taking off explosively only as a last resort. Plumage varies from dull to spectacular, and many species have ornamental crests or plumes on their heads. Moderate sexual dichromism is seen in plumage, with males having brighter plumage.