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Albatrosses
are among the most oceanic of sea- birds, coming ashore only to breed.
They have an
ancient lineage, with fossils dating back to the Eocene, some 50 million
years ago. Despite being
relatively well studied, albatross taxonomy is in a state of flux, with
anything from 14 to 24 recognised species. Although four species breed
in the tropical Pacific Ocean and fossil remains from Florida and the
United Kingdom show they used to occur in the North Atlantic, most
species are found in the Southern Ocean.
Between 40°S
and 65°S
here is an almost unbroken expanse of ocean circling the globe,
characterised by some the most persistent winds in the world.
It is here that the great albatrosses – the Wander and Royal
– ply their trade.
With a wingspan
of up to 3.5 meters, the Wandering Albatross is renowned as having the
longest wings of any living bird. Weighing
up to 12 kilograms (with an average of between 7 and 10 kilograms) they
are almost among the heaviest flying birds.
Wandering
Albatrosses range throughout the Southern Ocean, using their long,
slender wings to obtain a free ride from the prevailing winds.
In a technique known as dynamic soaring, the albatrosses and
their cousins, the petrels, use differences in wind speed between wave
troughs and crests to generate lift and speed without flapping.
In this way they can cover vast distances in search of prey, but
they pay a price in that they are restricted t only feeding within a meter
or two of the ocean surface. |
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Their long
wings trap a large volume of air, making them to buoyant to be efficient
divers. As a result,
Wandering Albatrosses are indiscriminate foragers, taking a wide range
of prey, including inappropriate items such a plastic litter and bait
lines. Squid comprise the
majority of the diet and most are probably found dead or moribund
because species that float when dead predominate the albatross’ diet.
In calm
weather, the Wandering Albatross has to work hard to stay aloft and with
its heavy, hunch-backed appearance, the bird is the cumbersome relative
of the smaller albatrosses or mollyhawks.
When the wind does fail, the Wanderers spend a large amount of time
sitting on the water – one satellite-tracked an individual who barely moved
for seven days when it was becalmed in a high-pressure cell.
The requirement for reliable wind prevents the Wandering
Albatross from Penetrating tropical waters and it is scarce north of 30°S.
Adult males are
totally white except for black tips on their wings.
Female birds often have a dark cape, with black specking on the
back and upper wing. Juveniles
are totally brown except for white under the wings and a conspicuous
white face mask. Immature birds grade from the brown juvenile to the
speckled female plumage.
They have been
recorded off the coast off the south western coast all the way around to
Inhambane on the East Coast.
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