Albatross in the context of "Chandler Robbins"

Bird migration is a seasonal movement of some birds between breeding and wintering grounds that occurs twice a year. It is typically from north to south or from south to north. Migration is inherently risky, due to predation and mortality.

The Arctic tern holds the long-distance migration record for birds, travelling between Arctic breeding grounds and the Antarctic each year. Some species of tubenoses, such as albatrosses, circle the Earth, flying over the southern oceans, while others such as Manx shearwaters migrate 14,000 km (8,700 mi) between their northern breeding grounds and the southern ocean. Shorter migrations are common, while longer ones are not. The shorter migrations include altitudinal migrations on mountains, including the Andes and Himalayas.

The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and has a mean transport estimated at 137 ± 7 Sverdrups (Sv, million m/s), or possibly even higher, making it the largest ocean current. The current is circumpolar due to the lack of any landmass connecting with Antarctica and this keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge ice sheet.

Associated with the Circumpolar Current is the Antarctic Convergence, where the cold Antarctic waters meet the warmer waters of the subantarctic, creating a zone of upwelling nutrients. These nurture high levels of phytoplankton with associated copepods and krill, and resultant food chains supporting fish, whales, seals, penguins, albatrosses, and a wealth of other species.

A bird colony is a large congregation of individuals of one or more species of bird that nest or roost in proximity at a particular location. Many kinds of birds are known to congregate in groups of varying size; a congregation of nesting birds is called a breeding colony. Colonial nesting birds include seabirds such as auks and albatrosses; wetland species such as herons; and a few passerines such as weaverbirds, certain blackbirds, and some swallows. A group of birds congregating for rest is called a communal roost. Evidence of colonial nesting has been found in non-neornithine birds (Enantiornithes), in sediments from the Late Cretaceous (Maastrichtian) of Romania.

A food bolus ( bolus Latin for 'ball') is a ball-like mixture of food and saliva that forms in the mouth during the process chewing in readiness for being swallowed. It has the same color as the food being eaten, and the saliva gives it an alkaline pH.

Under normal circumstances, the bolus is swallowed, and travels down the esophagus to the stomach for digestion. Sometimes a bolus may become lodged in the esophagus either due to the type of food being eaten or to changes in the esophagus itself, when it is known as an esophageal food bolus obstruction.

Vision is the most important sense for birds, since good eyesight is essential for safe flight. Birds have a number of adaptations which give visual acuity superior to that of other vertebrate groups; a pigeon has been described as "two eyes with wings". Birds are theropods, and the avian eye resembles that of other sauropsids, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, bird's eyes are protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the pecten oculi, unique to birds.

Some bird groups have specific modifications to their visual system linked to their way of life. Birds of prey have a very high density of receptors and other adaptations that maximise visual acuity. The placement of their eyes gives them good binocular vision enabling accurate judgement of distances. Nocturnal species have tubular eyes, low numbers of colour detectors, but a high density of rod cells which function well in poor light. Terns, gulls, and albatrosses are among the seabirds that have red or yellow oil droplets in the colour receptors to improve distance vision especially in hazy conditions.

The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the diving petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes (or tubenoses), which also includes the albatrosses and the storm petrels.

The procellariids are the most numerous family of tubenoses, and the most diverse. They range in size from the giant petrels with a wingspan of around 2.0 m (6 ft 7 in), that are almost as large as the albatrosses, to the diving petrels with a wingspan of around 34 cm (13 in) that are similar in size to the little auks or dovekies in the family Alcidae. Male and female birds are identical in appearance. The plumage colour is generally dull, with blacks, whites, browns and greys. The birds feed on fish, squid and crustacea, with many also taking fisheries discards and carrion. Whilst agile swimmers and excellent in water, petrels have weak legs and can only shuffle on land, with the giant petrels of the genus Macronectes being the only two species that are capable of proper terrestrial locomotion. All species are accomplished long-distance foragers, and many undertake long trans-equatorial migrations. They are colonial breeders, exhibiting long-term mate fidelity and site philopatry. In all species, a single white egg is laid each breeding season. The parents take it in turns to incubate the egg and to forage for food. The feeding area can be at a great distance from the nest site. The incubation times and chick-rearing periods are exceptionally long compared to other birds.

Procellariiformes /prɒsɛˈlɛəri.ɪfɔːrmiːz/ is an order of seabirds that comprises four families; the albatrosses, the petrels and shearwaters, and two families of storm petrels. Formerly called Tubinares and still called tubenoses in English, procellariiforms are often referred to collectively as the petrels, a term that has been applied to all members of the order, or more commonly all the families except the albatrosses. They are almost exclusively pelagic (feeding in the open ocean), and have a cosmopolitan distribution across the world's oceans, with the highest diversity being around New Zealand.

Procellariiforms are colonial, mostly nesting on remote, predator-free islands. The larger species nest on the surface, while most smaller species nest in natural cavities and burrows. They exhibit strong philopatry, returning to their natal colony to breed and returning to the same nesting site over many years. Procellariiforms are monogamous and form long-term pair bonds that are formed over several years and may last for the life of the pair. A single egg is laid per nesting attempt, and usually a single nesting attempt is made per year, although the larger albatrosses may only nest once every two years. Both parents participate in incubation and chick rearing. Incubation times are long compared to other birds, as are fledging periods. Once a chick has fledged there is no further parental care.