Faster wind speeds over Southern Ocean mean largest member of great albatross family is flying faster, improving its reproductive success. Over the last 50 years, westerlies in the southern hemisphere have tended to speed up and shift towards the South Pole

Wandering albatross gets boost from rising winds

by Catharine Brahic, NewScientist, January 12, 2012

It is a small comfort, given the dire effects climate change is having on birds worldwide, but industrial emissions may be giving the endangered wandering albatross a turbo boost.

Faster wind speeds over the Southern Ocean mean the largest member of the great albatross family is flying faster, which improves its reproductive success.

Famous for having the largest wingspan of any living bird, populations of the wandering albatross (Diomedea exulans) have crashed in recent decades. On the Crozet Islands in the southern Indian Ocean, home to the largest breeding population of the albatross, the number of birds dropped by 54% between 1976 and 1980. After briefly stabilising, the population of 2,000 breeding pairs is once more in decline.

Henri Weimerskirch and his colleagues at the Centre of Biological Studies of Chizé in Villiers-en-Bois, France, have been tracking the soaring giants of Crozet for decades. By combining 40 years of data on foraging trips, body mass and breeding success, with regional wind speed data, they discovered that environmental changes are having a curious – if temporary – effect on the colony.

Blow wind blow

Over the last 50 years, westerlies in the southern hemisphere have tended to speed up and shift towards the South Pole, a trend which has been linked to emissions of ozone-depleting chemicals, for example (Science, DOI: 10.1126/science.1087440). Some also suspect the hand of climate change, although they caution that it is too soon to say for sure.

So far Weimerskirch found that the albatrosses of Crozet have reaped the benefit. They spend much of their lives in the air and their soaring flight is heavily influenced by wind speeds. The birds moved faster in the last decade than in the 1990s, allowing them to shorten their foraging trips. They also shifted their foraging range into windier regions closer to the islands.

Shorter, foraging trips closer to home allowed the males and females – who share parental duties – to shorten their incubating shifts at the nest. And shorter shifts improve the parent's health, which correlate with healthier broods.

For the albatrosses, there is another advantage to foraging further south, nearer to the islands, say the researchers. So far, their greatest threat has come from longline tuna fishing: the birds are attracted to the bait, get caught on the lines and drown. But the southward shift is moving them away from the tuna fishing fleet.

But the change that took the team most by surprise, they say, was that both males and females have gained a kilogram on average in the last 20 years. This could have a big impact on the nature of their flight. Being heavier means they can exploit windier regions. Thus, the fact that the birds are putting on weight may in fact be an evolutionary adaptation to the environmental changes around them, says Weimerskirch.

But there's a sting to the story's tail. The team looked at forecasts of future wind patterns. Models predict that the poleward shift will carry on and winds will continue to get stronger. "Too strong gales of winds become unfavourable for dynamic soaring," the team warns. Foraging, they say, will eventually become more costly and the benefits of recent years will vanish.

The same, they warn, could hold true for many other species of albatross and for petrels too, whose movement is also constrained by wind patterns.

Journal reference: Science, DOI: 10.1126/science.1210270

http://www.newscientist.com/article/dn21349-wandering-albatross-gets-boost-from-rising-winds.html