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Feeding at sea
Most breeding birds share responsibility for incubation of their eggs and regularly take turns on the nest to allow each partner to feed. Once the young hatch, the parents travel back and forth to their nest many times a day with food.
Albatrosses, however, are completely different and spend many days feeding at sea, often thousands of miles away from the nest, before returning to their mate or chick.
So how on earth do they store all the food they have eaten?
Well, albatrosses and their relatives, petrels, have an upper stomach, or proventriculus, into which all of the food goes for initial digestion.
Squid, fish, krill and other items on the albatross menu are broken down into a mixture of water, fats, proteins and everything else. This mixture sperates into two parts; an oil layer which floats to the top and is retained in a special 'stomach', and water-soluble proteins and other compounds that settle to the bottom of the upper stomach.
The lower water layer passes out of the upper stomach into the lower gut where it then continues its journey to be digested and absorbed in the normal way, making room for more food. Only when the bird is finally full will it return to its island home.
The top oil layer is a ready source of energy and small amounts of it do trickle through to be fully digested by the parent. The rest is stored until the adult gets back to the nest and is then regurgitated as food for the youngster.
What do albatrosses eat?
Albatrosses feed mainly on fish and squid, catching them close to the ocean's surface. Krill, a shrimp-like crustacean, also form a large part of the diet of those species found in southern waters.
As albatrosses cannot dive down very far beneath the waters surface, they also scavenge for pieces of dead animals. For this reason, they are attracted to trawlers and other fishing vessels, as these are a regular source of discarded fish waste.
Albatrosses have a well developed sense of smell that enables them to detect food from a considerable distance.
When on a feeding trip, an albatross can cover an astonishing amount of ground, and the feeding ranges of most species cover thousands of square kilometres of ocean.
It has been estimated that the royal albatross of New Zealand can fly 1,800 km in 24 hours and may travel a staggering 320,000 km a year, while a grey-headed albatross was recorded circumnavigating the Southern Ocean covering a distance of 22,000 km in just 46 days.
Intruders beware
As well as being a great source of food, there is another use for the oil - defence. Both petrels and albatrosses regurgitate this foul-smelling oil from their stomachs as a means of protection.
Adult albatrosses rarely use this method, as they can ward off enemies with their beaks and wings. However, alarmed young chicks will readily eject large quantities of this half-digested food, coating any intruder in an evil-smelling and sticky fluid.
The oil sticks onto the fur, or feathers of a predator and is difficult to remove, causing loss of insulation and waterproofing properties that, in a cold and wet environment, can prove lethal.