On a Wing and a Prayer - Feature Article
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BAS monitors populations of three albatross species - the wandering albatross, the black-browed albatross and the grey-headed albatross - on Bird Island. Together with South Georgia, it is home to some of the largest colonies of these birds in the world. "The biggest global populations of grey-headed and light-mantled albatrosses are on South Georgia, which also has the second largest populations of wandering albatrosses and black-browed albatrosses, so South Georgia is a very important breeding site," Phillips explains.
"South Georgia albatross populations are among the best studied worldwide. For wandering albatross, BAS has a high intensity study area of about 120 pairs. We have ringed all the adults here and we monitor laying dates, egg size, hatching success, chick growth and fledging success. And from resighting adults in successive years we get an indication of how often they breed and of adult survival," Phillips says.
Sadly, the picture that this science paints is one of inexorably declining albatross numbers. According to Phillips: "The populations that are declining most rapidly are in the South Atlantic, breeding on the UK Overseas Territories. On South Georgia, the three species that BAS monitors are declining at between 2% and 5% a year."
Crucially in conservation terms, it is the satellite transmitters and tiny geolocators they attach to the birds that have given BAS scientists an unparalleled insight into why albatross populations are declining so dramatically.
Data from these devices show that the birds are feeding for the fish and squid on which they depend in the same areas in which fishing fleets operate. Both trawling and long-lining - where fishing vessels release lines containing thousands of baited hooks - are killing thousands of albatrosses each year. Attracted to the bait on the hooks, many albatrosses will swallow fishing hooks and drown behind long-line fishing vessels, while others will collide with trawler cables, breaking their wings and falling into the sea.
- Albatrosses belong to a group of birds known as Procellariiformes, or "tube noses". Tubes on the birds' beaks allow them get rid of excess salt - a crucial adaptation that means albatrosses can spend most of their lives at sea, free from the need to find fresh water.
- According to IUCN, there are 21 species of albatross and 19 of these are at risk of extinction.
- With wing spans of up to 3.5 metres, albatrosses are the largest of all seabirds. They are also the longest lived.
- Albatrosses mate for life and have among the lowest divorce rate of any bird.
- BirdLife International estimates that fishing fleets are killing around 100,000 albatrosses each year.
- Albatrosses cover vast distances when foraging for food, especially during breeding. Wandering albatrosses, for example, range from sub-tropical to Antarctic waters on trips covering up to 10,000 km in 10-20 days. Outside the breeding season, several species - such as the royal and wandering albatrosses - migrate long distances, some traveling right round the Earth.
But by understanding why, where and when the birds are being killed in such large numbers, scientists have been able to suggest ways in which fisheries can operate successfully at the same time as mitigating the impact on the albatrosses.
According to Phillips: "Once people realised long-lining was a threat, there was a lot of effort to develop different ways for mitigating that threat. You can have a streamer line flapping behind the vessel to discourage birds from trying to feed on the baited hooks. You can weight hooks so that they sink quickly below the surface and become inaccessible to birds. You can set the baits underwater, keep offal and waste bait on board so that you don't encourage birds to come to the boat in the first place, and set the lines during the night, when albatrosses don't usually feed. And around South Georgia, there's also a closed season, so they don't fish during the summer when the smaller species are vulnerable."
The success of these measures in eliminating so-called "by-catch" of albatrosses around South Georgia gives Phillips grounds for hope: "Around South Georgia during the late 1990s there were 6,000 seabirds being killed each year. But the introduction of the various mitigation measures, which were made mandatory by the South Georgia government, has been so successful that last year no birds were killed. It's an example of a very profitable fishery which has successfully introduced mitigation measures, and which was recently accorded Marine Stewardship Council certification in recognition of its high level of environmental sustainability and management."
The challenge now is to ensure that other fisheries follow suit. "What's unfortunate is that because these birds migrate vast distances, they still encounter fishing fleets in other areas of ocean that aren't using mitigation measures. What we have to do now is to persuade the Regional Fisheries Management Organisations - the big tuna commissions - to take a stronger approach to enforcing mitigation measures. Things are looking up, but as yet we haven't seen an upturn in the populations in the South Atlantic, so there's still a lot of work to be done," Phillips says.
Images © British Antarctic Survey / Words © Becky Allen.