Biology
Taxonomy and evolution
The albatrosses comprise between 13 and 24 species (the number of species is still a matter of some debate, 21 being the most commonly accepted number) in four genera. These genera are the great albatrosses (Diomedea), the mollymawks(Thalassarche), the North Pacific albatrosses (Phoebastria), and the sooty albatrosses or sooties (Phoebetria). 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.[3]
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 orderProcellariiformes. 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 (see below: Morphology and flight).[3]
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 (though never more than eight at one time) by 1965 (Diomedea, Phoebastria, Thalassarche, Phoebetria, Thalassageron, Diomedella, Nealbatrus, Rhothonia, Julietata, Galapagornis, Laysanornis, and Penthirenia).[4]
By 1965, in an attempt to bring some order back to the classification of albatrosses, they were lumped into two genera, Phoebetria (the sooty albatrosses which most closely seemed to resemble the procellarids and were at the time considered "primitive" ) and Diomedea (the rest).[5] Though there was a case for the simplification of the family (particularly the nomenclature), 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.[4]
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 14 accepted species, finding four, not two, monophyletic groups within the albatrosses.[6] 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.
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 ogenetic relationships of the albatross genera, based on Nunn et al., 1996 albatross genera, Robertson and Nunn went on in 1998 to propose a revised taxonomy with 24 different species,[4] 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 theAntipodean 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 (including the lumping of the Amsterdam albatross with the wandering albatross),[]although this paper was itself controversial. On all sides is the widespread agreement on the need for further research to clarify the issue.
Sibley and Ahlquist's molecular study of the evolution of the bird families has put the radiation of the Procellariiformes in the Oligoceneperiod (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 (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 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 (Middle Eocene of Uzbekistan), Manu(early Oligocene of New Zealand), and an undescribed form from the Late Oligocene of South Carolina. Similar to the last was Plotornis, formerly often considered a petrel but 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 byPhoebastria 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 (the North Pacific albatrosses); one, Phoebastria anglica, has been found in deposits in both North Carolina and England. Due toconvergent evolution in particular of the leg and foot bones, remains of the prehistoric pseudotooth birds (Pelagornithidae) 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. For more data on fossil species of the living albatross genera, see the genus articles.
Distribution and range at sea
Most albatrosses range in the Southern Hemisphere from Antarctica to Australia, South Africa and South America. The exceptions to this are 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 in the Galapagos Islands and feeds off the coast of South America. The need for wind to enable gliding is the reason albatrosses are for the most part confined to higher latitudes; being unsuited to sustained flapping flight makes crossing the doldrums extremely difficult. The exception, the waved albatross, is able to live in the equatorial waters around the Galapagos Islands because of the cool waters of the Humboldt Current and the resulting winds.[3]
It is not known for certain why the albatrosses became extinct in the North Atlantic, although rising sea levels due to an interglacialwarming period are thought to have submerged the site of a short-tailed albatross colony that has been excavated in Bermuda.[11] Some southern species have occasionally turned up as vagrants in the North Atlantic and can become exiled, remaining there for decades. One of these exiles, a black-browed albatross, returned to gannet colonies in Scotland for many years in an attempt to breed.[22]
The use of satellite tracking is teaching scientists a great deal about the way albatrosses forage across the ocean to find food. They undertake no annual migration, but disperse widely after breeding, in the case of Southern Hemisphere species, often undertaking circumpolar trips.[23] There is also evidence that there is separation of the ranges of different species at sea. A comparison of the foraging niches of two related species that breed on Campbell Island, the Campbell albatross and the grey-headed albatross, showed the Campbell albatross primarily fed over the Campbell Plateau whereas the grey-headed albatross fed in more pelagic, oceanic waters. Wandering albatrosses also react strongly to bathymetry, feeding only in waters deeper than 1000 m (3281 ft); so rigidly did the satellite plots match this contour that one scientist remarked, "It almost appears as if the birds notice and obey a 'No Entry' sign where the water shallows to less than 1000 m".[3] There is also evidence of different ranges for the two sexes of the same species; a study of Tristan albatrosses breeding on Gough Island showed that males foraged to the west of Gough and females to the east.
Diet
The use of data loggers at sea that record ingestion of water against time (providing a likely time of feeding) suggest that albatrosses 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 primarily comes from the die-off that occurs after squid spawning and the vomit of squid-eating whales (sperm whales, pilot whales and southern bottlenose whales).[24] The diet of other species, like theblack-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.[3] Also the waved albatross has been observed practising kleptoparasitism, harassing boobies to steal their food, making it the only member of its order to do so regularly.[25]The albatross diet is predominantly cephalopods, fish, crustaceans, and offal,[14] although they will also scavenge carrion and feed on other zooplankton.[14] It should be noted that for most species a comprehensive understanding of diet is known for only the breeding season, when the albatrosses regularly return to land and study is possible. The importance of each of these food sources 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.[14]
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, 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 albatross, have a mean diving depth of almost 5 m and can dive as deep as 12.5 m.[26] In addition to surface feeding and diving, they have also been observed plunge diving from the air to snatch prey.[27]
Breeding and dancing
Albatrosses live much longer than other birds; they delay breeding for longer and INVEST more effort into fewer young. Most species survive upwards of 50 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.[30] Given that most albatross ringing projects are considerably younger than that, it is thought likely that other species will prove to live that long and even longer.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. Many Buller's albatrossesand black-footed albatrosses nest under trees in open forest.[28] 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 and great 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 to their point of origin to breed is so strong that a study of Laysan albatross showed that the average distance between hatching site and the site where a bird established its own territory was 22 m (72 ft).[29]
Albatrosses reach sexual maturity slowly, after about five 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 attend a colony prior to beginning to breed, spending many years practising the elaborate breeding rituals and "dances" that the family is famous for.[31] 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.[14] 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).[32] When a bird first returns to the colony it will dance with many partners, but after a number of years the number of birds an individual will interact with drops, until one partner is chosen and a pair is formed. 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 again.
All the southern albatrosses create large nests for their egg, utilizing grass, shrubs, soil, peat, and even penguin feathers,[28] 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 (160 ft), sometimes causing it to lose the egg.[33] In all albatross species, both parents incubate the egg in stints that last between one day and three weeks. Incubation lasts around 70 to 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 (2.9 oz) of body weight a day.[34]Albatrosses are held to undertake these elaborate and painstaking rituals to ensure that the appropriate partner has been chosen and to perfect partner recognition, as egg laying and chick rearing is a huge INVESTMENT. Even species that can complete an egg-laying cycle in under a year seldom lay eggs in consecutive years.[3] The great albatrosses (like the wandering albatross) take over a year to raise a chick from laying to fledging. Albatrosses lay a single subelliptical[16] egg, white with reddish brown spots,[28] in a breeding season; if the egg is lost to predators or accidentally broken, then no further breeding attempts are made that year. The larger eggs weigh from 200 to 510 g (7.1–18.0 oz).[28] The "divorce" of a pair is a rare occurrence, due to the diminished life-time reproductive success it causes, and usually only happens after several years of breeding failure.[3]
Albatross chicks take a long time to fledge. In the case of the great albatrosses, it can take up to 280 days; even for the smaller albatrosses, it takes anywhere between 140 and 170 days.[36] Like many seabirds, albatross chicks will 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. Between 15% and 65% of those fledged survive to breed.[28] Albatross chicks fledge on their own and receive no further help from their parents, who 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, which helps young birds when they are first out at sea.[37]After hatching, the chick, which is semi-altricial,[16] is brooded and guarded for three weeks until it is large enough to defend andthermoregulate itself. During this period the parents feed the chick small meals 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 (21 oz)). The meals are composed of both fresh squid, fishand 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 most tubenoses, and gives them their distinctive musty smell.
Albatrosses and humans
Etymology
The name albatross is derived from the Arabic al-câdous or al-ġaţţās (a pelican; literally, "the diver"), which travelled to English via the Portuguese form alcatraz ("gannet"), which is also the origin of the name of the former prison, Alcatraz. The OED 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.[14] In modern Portuguese, the word used for the bird, albatroz, is in turn derived from English albatross.
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 wordprocella meaning "a violent wind" or "a storm".
In culture
In golf, shooting three under par on a single hole has recently been termed scoring an "albatross", as a continuation on the birdie and eagle theme.[41]Albatrosses have been described as "the most legendary of all birds".[36] An albatross is a central emblem in The Rime of the Ancient Mariner by Samuel Taylor Coleridge; a captive albatross is also a metaphor for the poète maudit in a poem of Charles Baudelaire. It is from the Coleridge poem that the usage of albatross as a metaphor is derived; someone with a burden or obstacle is said to have "an albatross around their neck", the punishment given in the poem to the mariner who killed the albatross. In part due to the poem, there is a widespread myth that (all) sailors believe it disastrous to shoot or harm an albatross; in truth, sailors regularly killed and ate them,[22] e.g., as reported by James Cook in 1772. On the other hand, it has been reported that sailors caught the birds, but supposedly let them free again;[39] the possible reason is that albatrosses were often regarded as the souls of lost sailors,[40] so that killing them was supposedly viewed as bringing bad luck.[39] The head of an albatross being caught with a hook is used as the emblem of the Cape Horners, i.e. sailors who have rounded Cape Horn on freighters under sail; captains of such ships even received themselves the title "albatrosses" in the Cape Horners' organisation.The Maori used the wing bones of the albatross to carve flutes.
