Albatross

? Albatross
Short-tailed Albatross
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Procellariiformes Family: Diomedeidae G.R. Gray, 1840
Genera
Diomedea Thalassarche Phoebastria Phoebetria

The albatrosses are seabirds in the family Diomedeidae, which is closely allied to the procellarids, storm-petrels and diving-petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic although fossil remains show they once occurred there too. Albatrosses are amongst the largest of flying birds, and the great albatrosses from the genus Diomedea have the largest wingspans of any extant birds.

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. Breeding pairs form over several years and will remain together for life. A breeding season can take over a year from laying to fledging, with a single egg laid in each breeding season.

Nineteen of the 21 species of albatrosses are threatened with extinction. Numbers of albatrosses have declined in the past due to harvesting for feathers, but today the albatrosses are threatened by introduced species such as rats and feral cats that attack eggs, chicks and nesting adults; by pollution; and by long-line fishing. Long-line fisheries pose the greatest threat, as feeding birds are attracted to the bait and become hooked on the lines and drown. Governments, conservation organisations and fishermen are all working towards reducing this by-catch.

Albatross biology

Distribution, evolution and taxonomy

The albatrosses comprise 21 species in 4 genera. The four genera are the great albatrosses (Diomedea), the mollymawks (Thalassarche), the North Pacific albatrosses (Phoebastria), and the sooty albatrosses or sooties (Phoebetria). Of the four genera, 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. All albatrosses range in the southern hemisphere except for the four North Pacific albatrosses, of which three occur exclusively in the North Pacific, from Hawaii to Japan, California and Alaska; and one, the Waved Albatross, breeds on the equator in the Galapagos Islands and feeds off the coast of South America.

The taxonomy of the albatross group has been a source of a great deal of debate. The Sibley-Ahlquist taxonomy places seabirds, birds of prey and many others in a greatly enlarged order Ciconiiformes, whereas the ornithological organisations in North America, Europe, South Africa, Australia and New Zealand retain the more traditional order Procellariiformes.

Within the family, the assignment of genera has been debated for over a hundred years. Originally placed into a single genus, Diomedea, they were split into four different genera in 1852, then lumped back together and split again several times, acquiring 12 different genus names in total (though never more than 8 at one time) by 1965 (Diomedea, Phoebastria, Thalassarche, Phoebetria, Thalassageron, Diomedella, Nealbutrus, Rhothonia, Julietata, Galapagornis, Laysanornis, and Penthirenia).

By 1965, in an attempt to bring some order back to the classification of albatrosses they were lumped into two genera, Phoebetria (the 'primitive' sooty albatrosses which most closely seemed to resemble the procellarids) and Diomedea (the rest). Though there was a case for the simplification of the family (particularly the nomenclature), the classification was pretty much the same as suggested by Elliott Coues in 1866, paid little attention to more recent studies and even ignored some of Coues's suggestions.

More recent research by Gary Nunn of the American Museum of Natural History ( 1996) and other researchers around the world studied the mitochondrial DNA of all the 14 accepted species, finding that there were 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. Both the British Ornithologists' Union and the South African authorities split the albatrosses into four genera as Nunn suggested, and the change has been accepted by the majority of researchers as well.

While there is some agreement on the number of genera, there is less agreement on the number of species. After his work on albatross genera, Nunn went on to propose 24 different species in 1998, compared to the 14 then accepted. These changes were not universally accepted; some of his splits have been accepted while others have been rejected and for the most part 21 species is the number accepted by the IUCN and many others (though by no means not all—two authors have called for the number of species to be returned to 14).

The molecular study of the evolution of the bird families by Sibley and Ahlquist has put the radiation of the Procellariiformes in the Oligocene period (35–30 million years ago), though the group has an older history, with a fossil attributed to the order, a seabird known as Tytthostonyx, being found in late Cretaceous rocks (70 mya). 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. The earliest fossil albatross was found in South Carolina in rocks dating from the Upper Oligocene, though it is uncertain which genus it should be attributed to. The four genera are believed to have split more recently; a fossil albatross attributed to the North Pacific albatrosses, Phoebastria californica was found in mid Miocene rocks in California, showing 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. 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 (the North Pacific albatrosses), although one great albatross, Diomedea anglica, has been found in deposits in both North Carolina and England. It is not known for certain why the albatrosses became extinct in the North Atlantic, although rising sea levels due to an interglacial warming period are thought to have submerged the Short-tailed Albatross colony found in Bermuda .

Morphology and flight

The albatrosses are a group of large to very large birds with very long narrow wings, which are aerodynamically highly efficient. The wingspans of the largest great albatrosses (genus Diomedea) are the largest of any bird, exceeding 340 cm, although the other species' wingspans are considerably smaller.

The bill is large, strong and sharp-edged, 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 name. These tubes allow the albatrosses to have an acute sense of smell, an unusual ability for birds. Like other Procellariiformes they use this olfactory ability while foraging in order to locate potential food sources. The feet have no hind toe, and the three anterior toes are completely webbed. The legs are strong for Procellariiformes, in fact uniquely amongst the order in that they and the giant petrels are able to walk well on land.

Albatrosses travel huge distances with two techniques used by many long-winged seabirds, dynamic soaring and slope soaring. Dynamic soaring enables them to minimise the effort needed by gliding across wave fronts gaining energy from the vertical wind gradient. Slope soaring is more straightforward, the albatross turns to the wind, gaining height, from where it can then glide back down to the sea. Albatross have high glide ratios, around 22:23, meaning that for every metre they drop they can travel forwards 22 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 up and out 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 will take a clockwise route and those flying south will fly anticlockwise. 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, takeoffs and hunting they undertake having found a food source. This efficient long distance travelling underlies the albatross's success as a long distance forager.

The need for wind in order to glide is the reason albatrosses are for the most part confined to higher latitudes, since they are unsuited to sustained flapping flight, and are usually incapable of crossing the doldrums. Some southern species that have occasionally turned up as vagrants in the North Atlantic have essentially become exiled and can remain in the North Atlantic for decades. One of these exiles, a Black-browed Albatross, returned to gannet colonies in Scotland for many years in a lonely attempt to breed.

Diet

The albatross diet is dominated by cephalopods, fish and crustaceans, although they will also scavenge carrion and feed on other zooplankton. It should be noted that for most species a comprehensive understanding of diet is only known for the breeding season, when the albatrosses are on land and study is possible. The importance of each of these varies from species to species, and even from population to population, some concentrate on squid alone, others take more krill, or fish. Of the two albatross species found in Hawaii, one, the Black-footed Albatross takes mostly fish while the Laysan feeds on squid.

The use of dataloggers at sea that record ingestion of water against time (providing a likely time of feeding) suggest that albatross predominantly feed during the day. Analysis of the squid beaks regurgitated by albatrosses has shown that many of the squid eaten are too large to have been caught alive, and include mid-water species likely to be beyond the reach of albatross, suggesting that, for some species (like the Wandering Albatross), scavenged squid may be an important part of the diet. The source of these dead squid is a matter of debate, some certainly comes from squid fisheries, but in nature it probably came from the die-off that occurs after squid spawning and the vomit of squid-eating whales ( sperm whales, pilot whales and Southern Bottlenose Whales), or possibly some other source. The diet of other species, like the Black-browed Albatross or the Grey-headed Albatross, is rich with smaller species of squid that tend to sink after death, and scavenging is not assumed to play a large role in their diet.

Until recently it was thought that albatross were predominantly surface feeders, swimming at the surface and snapping up squid and fish pushed to the surface by currents, other predators or death. The deployment of capillary depth recorders, which record the maximum dive depth undertaken by a bird (between attaching it to a bird and recovering it when it returns to land), has shown that while some species, like the Wandering Albatross, do not dive deeper than a metre, some species, like the Light-mantled Sooty Albatross, have a mean diving depth of almost 5m and can dive as deep as 12.5 m . In addition to surface feeding and diving they have now also been observed plunge diving from the air to snatch prey.

Breeding

Albatrosses are colonial, usually nesting on isolated islands; where colonies are on larger landmasses they are found on exposed headlands with good approaches from the sea in several directions, like the colony on the Otago Peninsula in Dunedin, New Zealand. Colonies vary from the very dense aggregations favoured by the mollymawks ( Black-browed Albatross colonies on the Falkland Islands have densities of 70 nests per 100 m²) to the much looser groups and widely spaced individual nests favoured by the sooty albatrosses. All albatross colonies are on islands that historically were free of land mammals. Albatrosses are highly philopatric, meaning they will usually return to their natal colony to breed. This tendency to return is so strong that a study of Laysan Albatross showed that that average distance between hatching site and the site a bird established its own territory was 22 m.

Like most seabirds, albatrosses are K-selected with regard to their life-history, meaning they live much longer than other birds, they delay breeding for longer, and invest more effort into fewer young. Albatrosses are very long lived. Most species survive upwards of 60 years, the oldest recorded being a Northern Royal Albatross that was ringed as an adult and survived for another 51 years, giving it an estimated age of 61. Given that most albatross ringing projects are considerably younger than that, is seems likely that other species will prove to live that long and even longer.

Albatrosses reach sexual maturity slowly, after about 5 years, but even once they have reached maturity they will not begin to breed for another couple of years (even up to 10 years for some species). Young non-breeders will still attend a colony prior to beginning to breed, spending many years practicing the elaborate breeding rituals and "dances" that the family is famous for. Birds arriving back at the colony for the first time already have the stereotyped behaviours that compose albatross language, but can neither "read" that behaviour as exhibited by other birds nor respond appropriately. After a period of trial and error learning, the young birds learn the syntax and perfect the dances. This language is mastered more rapidly if the younger birds are around older birds.

The repertoire of behaviour involves synchronised performances of various actions such as preening, pointing, calling, bill clacking, staring, and combinations of such behaviours (like the sky-call). As they progress the number of birds they interact with drops until they choose one partner. They then continue to perfect an individual language that will eventually be unique to that one pair. Having established a pair bond that will last for life, however, most of that dance will never be used ever again. The 'divorce' of a pair is a rare occurrence, usually only happening after several years of breeding failure.

The reason for the elaborate and painstaking rituals is to ensure that the correct partner has been chosen, and to perfect recognition of their partner, as egg laying and chick rearing is a huge investment, and even species that can complete an egg-laying cycle in under a year seldom lay eggs in consecutive years. The great albatrosses (like the Wandering Albatross) take over a year to raise a chick from laying to fledging. Albatrosses lay a single egg; if the egg is lost to predators or accidentally broken then no further breeding attempts are made that year.

All the southern albatrosses create large nests for their egg, whereas the three species in the north Pacific make more rudimentary nests. The Waved Albatross, on the other hand, makes no nest and will even move its egg around the pair's territory, as much as 50 m, sometimes causing it to lose the egg. In all albatrosses species both parents incubate the egg, in stints that last between one day to three weeks. Incubation lasts around 70–80 days (longer for the larger albatrosses), the longest incubation period of any bird. It can be an energetically demanding process, with the adult losing as much as 83 g of body weight a day.

After hatching the chick is brooded and guarded for three weeks until it is large enough to defend and thermoregulate itself. During this period the chick is fed regularly with small meals by its parents when they relieve each other from duty. After the brooding period is over the chick is fed in regular intervals by both parents. The parents adopt alternative patterns of short and long foraging trips, providing meals that weigh around 12% of their body weight (around 600 g). The meals are composed of both fresh squid, fish and krill, as well as stomach oil, an energy-rich food that is lighter to carry than undigested prey items. This oil is created in a stomach organ known as a proventriculus from digested prey items by all tubenoses, and gives them their distinctive musty smell.

Albatross chicks take a long time to fledge. In the case of the great albatrosses it can up to 280 days, even for the smaller albatrosses it takes anywhere between 170 and 140 days. Like many seabirds, albatross chicks will actually gain enough weight to be heavier than their parents, and prior to fledging they use these reserves to build up body condition (particularly growing all their flight feathers), usually fledging at the same weight as their parents. Albatross chicks fledge on their own, and receive no further help from their parents, who will actually return to the nest after fledging, unaware their chick has left. Studies of juveniles dispersing at sea have suggested an innate migration behaviour, a genetically coded navigation route, that helps young birds first at sea.

Albatrosses and humans

Etymology

The name albatross is derived from the Arabic al-câdous, (a pelican), which travelled to English via the Portuguese form Alcatraz. The OED notes that the word alcatraz was originally applied to the frigatebird; the modification to albatross was perhaps influenced by Latin alba 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.

Albatrosses and culture

Albatrosses have been described as "the most legendary of all birds". They feature prominently in poetry such as the Samuel Taylor Coleridge poem The Rime of the Ancient Mariner. In part due to the poem, there is a widespread myth that sailors believe it disastrous to shoot or harm an albatross; in truth, however, sailors regularly killed and ate them. But they were often regarded as the souls of lost sailors. More recently they have become part of popular culture, for example, in a Monty Python sketch, or the song Echoes by Pink Floyd. In the movie Serenity, the character River was refered to as an albatross by The Operative, in the context of Coleridge's poem.

Threats and conservation

In spite of often being accorded legendary status by people albatrosses have not escaped both indirect and direct pressure from humanity. Early encounters with albatrosses by Polynesians and Aleut Indians resulted in hunting and in some cases expiration from some islands (such as Easter Island). As Europeans began sailing the world they too began to hunt albatross, "fishing" for them from boats to serve at the table or blasting them for sport. This sport reached its peak on emigration lines bound for Australia, and only died down when ships became too fast to fish from, and regulations stopped the discharge of weapons for safety reasons. In the 19th century, albatross colonies, particularly those in the North Pacific, were harvested for the feather trade, leading to the near extinction of the Short-tailed Albatross.

According to the IUCN Red List, 19 of the 21 albatross species are considered to have a conservation status as vulnerable or worse, partially due to the impact of commercial long-line fishing, as the albatrosses and other seabirds are attracted to the set bait, become hooked on the lines and drown. The scale of the problem is made worse by pirate fisheries, and an estimated 100,000 albatross are killed a year in this fashion. Two species (as recognised by the IUCN) are considered critically endangered, the Amsterdam Albatross and the Chatham Albatross.

Another threat to albatrosses is introduced species, which can be predators, like rats or feral cats, directly attacking the albatross or its chicks and eggs; or they can have indirect effects, cattle overgrazed essential cover on Amsterdam Island; on other islands introduced plants reduce potential nesting habitat.

Ingestion of floating plastic flotsam is another problem, one faced by many seabirds. The amount of plastic in the seas has increased dramatically since the first record in the 1960s, coming from waste discarded by ships, offshore dumping, litter on beaches and waste washed to sea by rivers. It is impossible to digest and takes up space in the stomach or gizzard that should be used for food, or can cause an obstruction that starves the bird directly. Studies of birds in the North Pacific have shown that ingestion of plastics results in declining body weight and body condition. This plastic is sometimes regurgitated and fed to chicks; a study of Laysan Albatross chicks on Midway Atoll showed large amounts of ingested plastic in naturally dead chicks compared to healthy chicks killed in accidents. While not the direct cause of death, this plastic caused physiological stress and caused the chick to feel full during feedings, reducing its food intake and reducing the chances of survival.

Scientists and conservationists (most importantly BirdLife International and their partners, who have run a Save the Albatross campaign) are working with governments and fishermen to find solutions to the threats albatrosses face. Techniques such as setting long-line bait at night, dying the bait blue, setting the bait underwater, increasing the amount of weight on lines and using bird scarers can all reduce the by-catch in seabirds by fishing fleets. For example, a collaborative study between scientists and fishermen in New Zealand successfully tested a underwater setting device for long-liners which set the lines below the reach of vulnerable albatross species. The use of some of these techniques in the Patagonian Toothfish fishery in the Falkland Islands is thought to have reduced the number of Black-browed Albatross taken by the fleet in the last 10 years. Conservationists have also worked on the field of island restoration, removing introduced species that threaten native wildlife, which protects albatrosses from introduced predators.

One important step towards protecting albatrosses and other seabird is the 2001 treaty the Agreement on the Conservation of Albatrosses and Petrels, which came into force in 2004 and has been ratified by eight countries, Australia, Ecuador, New Zealand, Spain, South Africa, France, Peru and the United Kingdom. This treaty requires specific actions to be taken by these countries to reduce by-catch, pollution and remove introduced species from nesting islands. The treaty has also been signed but not ratified by another three countries, Argentina, Brazil and Chile.

Species

Current thinking divides the albatrosses into four genera. The number of species is a matter of some debate, the IUCN and BirdLife International among others recognise 21 species, other authorities retain the more traditional 14 species:

• Great albatrosses (Diomedea)
  • Wandering Albatross D. exulans
  • Antipodean Albatross D. (exulans) antipodensis
  • Amsterdam Albatross D. amsterdamensis
  • Tristan Albatross D. (exulans) dabbenena
  • Northern Royal Albatross D. (epomorpha) sanfordi
  • Southern Royal Albatross D. epomophora

• North Pacific albatrosses (Phoebastria)
  • Waved Albatross P. irrorata
  • Short-tailed Albatross P. albatrus
  • Black-footed Albatross P. nigripes
  • Laysan Albatross P. immutabilis

• Mollymawks (Thalassarche)
  • Black-browed Albatross T. melanophris
  • Campbell Albatross T. (melanophris) impavida
  • Shy Albatross T. cauta
  • Chatham Albatross T. (cauta) eremita
  • Salvin's Albatross T. (cauta) salvini
  • Grey-headed Albatross T. chrysostoma
  • Atlantic Yellow-nosed Albatross T. chlororhynchos
  • Indian Yellow-nosed Albatross T. (chlororhynchos) carteri
  • Buller's Albatross T. bulleri

• Sooty albatrosses (Phoebetria)
  • Dark-mantled Sooty Albatross P. fusca
  • Light-mantled Sooty Albatross P. palpebrata.