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Bird Island is just 4 km long and 1 km wide and lies at the northwestern tip of the much larger island of South Georgia, near the confluence of the South Atlantic and Southern Oceans. The nearest inhabited land masses are the Falkland Islands and South America to the west of here. At the moment it is the summer in the southern hemisphere and the islands are surprisingly green, being covered in dense stands of tussock grass. In a few month however, the snow and ice will return, belying the close proximity of South Georgia to the Antarctic continent, to the south.
The reason for BAS having a research station here is because Bird Island is a mecca for migratory sea birds, such as albatrosses and penguins and marine mammals like fur seals. During the breeding season the island provides each with a small patch of terra firma on which to lay an egg or give birth to a pup. In summer it soon becomes a huge a crèche, while the adults go off to search for food for their young in the highly rich waters of the surrounding ocean. Four species of albatross breed here; the largest of all, the wandering albatrosses and the smallest, light-mantled sooty albatrosses as well as the mollymawks; grey-headed and black-browed albatrosses.
It is the last of these, the black-broweds, that I am most interested in, because not only are they the most common species (world population 1 – 3 million) but are also one the most threatened. Around South Georgia the population has declined by an alarming 30% over the past twenty years, putting the species firmly on the road to extinction. The cause of this decline is thought to be bycatch (that is accidental catch) by longline fishing boats. Longlining involves streaming a line of baited hooks out behind the fishing boat. As the hooks are put out albatrosses and other seabirds grab the bait, get caught on the hooks and drown. This problem can be avoided by fishermen taking a few simple precautions, which they do in regulated fisheries like the one around South Georgia. The problem is that albatrosses travel phenomenal distances, flying 100s – 1000s km in just a few days, sometimes at speeds in excess of 100 km/h, to find food for their young. This brings them into contact with many distant, unregulated fisheries.
In light of this crisis, my research aims to find out where these remarkable birds go to find food for their young and where they are likely to go when they are not breeding. Firstly, this means tracking the birds. That is what I am doing on Bird Island at the moment, attaching small GPS loggers to the birds before they set out to find food and then catching the them to get the data back when they return. The GPS loggers themselves are tiny; they are about the size of a box of matches and weight 30 g, while black-browed albatrosses have a 2.5-meter wing span and weigh around 3.5 kg. They use the same technology as the satnav systems many people now have in their cars, allowing us to follow the birds accurately as they search vast areas of the sea for food.
At the same time as doing my tracking work I shall be gathering data from a whole constellation of other satellites orbiting the Earth, which are recording things like the weather, the currents and temperature of the sea and even how much green plankton is growing in the areas visited by the birds. Albatrosses, like sailors rely on the wind to get around, which means that they can get to some places far more easily than others so the next step will be to look at this data and see which areas the albatrosses could theoretically have reached from Bird Island. Then I will compare these areas to the that they actually did visit so that I can find out what factors make for really good albatross feeding habitat. Finally, this knowledge I hope will allow me to predict where all the tens of thousands of albatrosses that we can’t track are likely to be going to feed so that conservationists and governments can concentrate their efforts on protecting these oceanic ‘hot spots’ form unnecessarily destructive fishing practices.
GPS tracking black-browed albatrosses, Bird Island, 2008. Ewan Wakefield
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Next report: Tagged Albatross flies some 300/400 miles for a single meal