Albatross
Albatrosses, of the biological family Diomedeidae, are large seabirds related to the procellariids, storm petrels, and diving petrels in the order Procellariiformes. They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic, although fossil remains of short-tailed albatross show they lived there up to the Pleistocene, and occasional vagrants are found. Great albatrosses are among the largest of flying birds, with wingspans reaching up to and bodies over in length. The albatrosses are usually regarded as falling into four genera, but disagreement exists over the number of species.
Albatrosses are highly efficient in the air, using dynamic soaring and slope soaring to cover great distances with little exertion. They feed on squid, fish, and krill by either scavenging, surface seizing, or diving. Albatrosses are colonial, nesting for the most part on remote oceanic islands, often with several species nesting together. Pair bonds between males and females form over several years, with the use of "ritualised dances", and last for the life of the pair. A breeding season can take over a year from laying to fledging, with a single egg laid in each breeding attempt. A Laysan albatross named Wisdom on Midway Island is the oldest-known wild bird in the world. She was first banded in 1956 by Chandler Robbins.
Of the 22 species of albatrosses recognised by the IUCN, 21 are listed as at some level of concern. Two species are Critically Endangered, seven species are Endangered, six species are Vulnerable, and six species are Near Threatened. Populations have declined in the past due to harvesting for feathers. Albatrosses are threatened by introduced species, such as rats and feral cats that attack eggs, chicks, and nesting adults; by pollution; by a serious decline in fish stocks in many regions largely due to overfishing; and by longline fishing. Longline fisheries pose the greatest threat, as birds are attracted to the bait, become hooked on the lines, and drown. Stakeholders such as governments, conservation organisations, and people in the fishing industry are all working toward reducing this phenomenon.
Etymology
The name "Albatross" is derived from the Arabic al-qādūs القادوس or al-ḡaṭṭās الغطاس, which travelled to English via the Portuguese form Alcatraz القطرس, which is also the origin of the name of the former prison Alcatraz. The Oxford English Dictionary notes that the word Alcatraz was originally applied to the frigatebird; the modification to albatross was perhaps influenced by Latin Albus, meaning "white", in contrast to frigatebirds, which are black.They were once commonly known as goonie birds or gooney birds, particularly those of the North Pacific. In the Southern Hemisphere, the name mollymawk is still well established in some areas, which is a corrupted form of malle-mugge, an old Dutch name for the northern fulmar. The name Diomedea, assigned to the albatrosses by Linnaeus, references the mythical metamorphosis of the companions of the Greek warrior Diomedes into birds. Finally, the name for the order, Procellariiformes, comes from the Latin word procella meaning "a violent wind" or "a storm".
File:Black-browed Albatross skeleton.jpg|thumb|Skeleton of a black-browed albatross on display at the Museum of Osteology in Oklahoma City, Oklahoma, U.S.
Taxonomy and evolution
The "albatross" designation comprises between 13 and 24 species in four genera. These genera are the great albatrosses, the mollymawks, the North Pacific albatrosses, and the sooty albatrosses or sooties. The North Pacific albatrosses are considered to be a sister taxon to the great albatrosses, while the sooty albatrosses are considered closer to the mollymawks.The taxonomy of the albatross group has been a source of much debate. The Sibley-Ahlquist taxonomy places seabirds, birds of prey, and many others in a greatly enlarged order, the Ciconiiformes, whereas the ornithological organisations in North America, Europe, South Africa, Australia, and New Zealand retain the more traditional order Procellariiformes. The albatrosses can be separated from the other Procellariiformes both genetically and through morphological characteristics, size, their legs, and the arrangement of their nasal tubes.
Within the family, the assignment of genera has been debated for over 100 years. Originally placed into a single genus, Diomedea, they were rearranged by Reichenbach into four different genera in 1852, then lumped back together and split apart again several times, acquiring 12 different genus names in total by 1965.
By 1965, in an attempt to bring some order back to the classification of albatrosses, they were lumped into two genera, Phoebetria and Diomedea. Though a case was made for the simplification of the family, the classification was based on the morphological analysis by Elliott Coues in 1866, and paid little attention to more recent studies and even ignored some of Coues's suggestions.
Research by Gary Nunn of the American Museum of Natural History and other researchers around the world studied the mitochondrial DNA of all 14 accepted species, finding four, not two, monophyletic groups within the albatrosses. They proposed the resurrection of two of the old genus names, Phoebastria for the North Pacific albatrosses and Thalassarche for the mollymawks, with the great albatrosses retaining Diomedea and the sooty albatrosses staying in Phoebetria.
While some agree on the number of genera, fewer agree on the number of species. Historically, up to 80 different taxa have been described by different researchers; most of these were incorrectly identified juvenile birds.
Based on the work on albatross genera, Robertson and Nunn went on in 1998 to propose a revised taxonomy with 24 different species, compared to the 14 then accepted. This expanded taxonomy elevated many established subspecies to full species, but was criticised for not using, in every case, peer reviewed information to justify the splits. Since then, further studies have in some instances supported or disproved the splits; a 2004 paper analysing the mitochondrial DNA and microsatellites agreed with the conclusion that the Antipodean albatross and the Tristan albatross were distinct from the wandering albatross, per Robertson and Nunn, but found that the suggested Gibson's albatross, Diomedea gibsoni, was not distinct from the Antipodean albatross. For the most part, an interim taxonomy of 21 species is accepted by ITIS and many other researchers, though by no means all—in 2004 Penhallurick and Wink called for the number of species to be reduced to 13, although this paper was itself controversial.
Sibley and Ahlquist's molecular study of the evolution of the bird families has put the radiation of the Procellariiformes in the Oligocene period 35–30 million years ago, though this group probably originated earlier, with a fossil sometimes attributed to the order, a seabird known as Tytthostonyx, being found in late Cretaceous rocks. The molecular evidence suggests that the storm petrels were the first to diverge from the ancestral stock, and the albatrosses next, with the procellarids and diving petrels separating later. The earliest fossil albatrosses were found in Eocene to Oligocene rocks, although some of these are only tentatively assigned to the family and none appear to be particularly close to the living forms. They are Murunkus, Manu, and an undescribed form from the Late Oligocene of South Carolina. The oldest widely accepted fossil albatross is Tydea septentrionalis from the early Oligocene of Belgium. Diomedavus knapptonensis is smaller than all extant albatrosses and was found in late Oligocene strata of Washington State, U.S. Plotornis was formerly often considered a petrel but is now accepted as an albatross. It is from the Middle Miocene of France, a time when the split between the four modern genera was already underway as evidenced by Phoebastria californica and Diomedea milleri, both being mid-Miocene species from Sharktooth Hill, California. These show that the split between the great albatrosses and the North Pacific albatrosses occurred by 15 Mya. Similar fossil finds in the Southern Hemisphere put the split between the sooties and mollymawks at 10 Mya.
The fossil record of the albatrosses in the Northern Hemisphere is more complete than that of the Southern, and many fossil forms of albatross have been found in the North Atlantic, which today has no albatrosses. The remains of a colony of short-tailed albatrosses have been uncovered on the island of Bermuda, and the majority of fossil albatrosses from the North Atlantic have been of the genus Phoebastria ; one, Phoebastria anglica, has been found in deposits in both North Carolina and England. Due to convergent evolution in particular of the leg and foot bones, remains of the prehistoric pseudotooth birds may be mistaken for those of extinct albatrosses; Manu may be such a case, and quite certainly the supposed giant albatross femur from the Early Pleistocene Dainichi Formation at Kakegawa, Japan, actually is from one of the last pseudotooth birds. Aldiomedes angustirostris was a uniquely narrow-beaked species from the Pliocene of New Zealand.
Morphology and flight
The albatrosses are a group of large to very large birds; they are the largest of the Procellariiformes. The bill is large, strong, and sharp-edged, with the upper mandible terminating in a large hook. This bill is composed of several horny plates, and along the sides are the two "tubes", long nostrils that give the order its former name. The tubes of all albatrosses are along the sides of the bill, unlike the rest of the Procellariiformes, where the tubes run along the top of the bill.Albatrosses, along with all Procellariiformes, must excrete the salts they ingest in drinking sea water and eating marine invertebrates. All birds have an enlarged nasal gland at the base of the bill, above their eyes. This gland is inactive in species that do not require it, but in the Procellariiformes, it acts as a salt gland. Scientists are uncertain as to its exact processes, but do know in general terms that it removes salt by secreting a 5% saline solution that drips out of the nose tubes or is forcibly ejected.
Like other Procellariiformes, they use their uniquely developed sense of smell to locate potential food sources, whereas most birds depend on eyesight.
The feet have no hind toe and the three anterior toes are completely webbed. The legs are strong for the Procellariiformes, making them and the giant petrels the only members of that order that can walk well on land.
The adult plumage of most of the albatrosses is usually some variation of dark upper-wing and back with white undersides, often compared to that of a gull. The extent of colouration varies: the southern royal albatross is almost completely white except for the ends and trailing edges of the wings in fully mature males, while the Amsterdam albatross has an almost juvenile-like breeding plumage with a great deal of brown, particularly a strong brown band around the chest. Several species of mollymawks and North Pacific albatrosses have face markings like eye patches or have grey or yellow on the head and nape. Three albatross species, the black-footed albatross and the two sooty albatrosses, vary completely from the usual patterns and are almost entirely dark brown. Albatrosses take several years to get their full adult breeding plumage.
The wingspans of the largest great albatrosses are the largest of any bird, exceeding, although the other species' wingspans are considerably smaller, at as low as. The wings are stiff and cambered, with thickened, streamlined leading edges. Albatrosses travel long distances with two techniques used by many long-winged seabirds – dynamic soaring and slope soaring. Dynamic soaring involves repeatedly rising into wind and descending downwind, thus gaining energy from the vertical wind gradient. The only effort expended is in the turns at the top and bottom of every such loop. This maneuver allows the bird to cover almost without flapping its wings. Slope soaring uses the rising air on the windward side of large waves.
Albatross have high glide ratios, around 22:1 to 23:1, meaning that for every metre they drop, they can travel forward twenty-two metres. They are aided in soaring by a shoulder-lock, a sheet of tendon that locks the wing when fully extended, allowing the wing to be kept outstretched without any muscle expenditure, a morphological adaptation they share with the giant petrels.
Albatrosses combine these soaring techniques with the use of predictable weather systems; albatrosses in the Southern Hemisphere flying north from their colonies take a clockwise route, and those flying south fly counterclockwise. Albatrosses are so well adapted to this lifestyle that their heart rates while flying are close to their basal heart rate when resting. This efficiency is such that the most energetically demanding aspect of a foraging trip is not the distance covered, but the landings, take-offs and hunting they undertake having found a food source. A common assumption is that Albatrosses must be able to sleep in flight, although no direct evidence has ever been obtained.
This efficient long-distance travelling underlies the albatross's success as a long-distance forager, covering great distances and expending little energy looking for patchily distributed food sources. Their adaptation to gliding flight makes them dependent on wind and waves, but their long wings are ill-suited to powered flight and most species lack the muscles and energy to undertake sustained flapping flight. Albatrosses in calm seas rest on the ocean's surface until the wind picks up again as using powered flight is not energetically worthwhile, though they are capable of flight to avoid danger. The North Pacific albatrosses can use a flight style known as flap-gliding, where the bird progresses by bursts of flapping followed by gliding. When taking off, albatrosses need to take a run up to allow enough air to move under the wing to provide lift.
The dynamic soaring of albatrosses has provided inspiration to airplane designers; German aerospace engineer Johannes Traugott and colleagues have charted the albatross's nuanced flight pattern and are looking for ways to apply this to aircraft, especially in the area of drones and unmanned aircraft.