wind and waves | 113near the Antarctic Polar Front and the outward journey is aided by a
following current.^3 It is uncertain whether the penguins head south be-
cause that takes them to the best feeding areas, or to take advantage of
the current. The fact that they can return home into the current with-
out undue difficulty might support the former explanation.
If a penguin porpoising epitomizes the frantic bustle of life, its an-
tithesis is a languid albatross. Wedged towards the stern of a 5,000- tonne
research ship, I first saw a Wandering Albatross on a journey from Cape
Town to Marion Island, 2,000 km to the south- east. From the grey dis-
tance the bird emerged. For perhaps 30 minutes, it planed above the
ship’s churning wake, hoping for a garbage snack. Not once were its
immense drooping wings flapped. But they were continuously adjusted,
just as a leading racing driver is forever twitching the steering wheel in
an effort to retain the fastest, racing line. The adjustments were most
obvious when the bird swooped to near the surface, perhaps even brush-
ing the water with a wing tip.
Sailors and biologists have long been fascinated by the ability of alba-
trosses to glide for hours with barely any movement of their wings. A
key factor is anatomical; a shoulder lock in albatrosses and giant petrels
has the effect of reducing or even eliminating the need for any muscle
power to hold the wing outstretched and horizontal. This occurs be-
cause, when the wing is fully extended, the lock resists any attempt to
raise the wing above the horizontal. As soon as the humerus is slightly
retracted from the fully forward position, the lock no longer operates,
and so the wing can be raised above the horizontal. A related anatomical
adaptation is the bulk of albatross flight muscles. They are smaller, rela-
tive to body size, than those of smaller flapping species, and the supra-
coracoideus muscle used to raise the wing during an upstroke is espe-
cially small. With less muscle mass to keep airborne, the gliding albatross
saves energy.
Albatrosses glide with wings locked for long periods using one of two
techniques. The first and more straightforward involves slope- soaring.
Wind is deflected upwards from the windward side of waves. If an al-
batross turns into this wind, it gains height, albeit with some loss of
ground speed, just as a para glider can gain height over land as wind is
deflected upwards off a hillside. Having gained height, the albatross can