Sunday 18 September 2011

Little auks go to the Greenland Sea to moult

Sophisticated tracking technology has revealed for the first time where little auks go straight after the summer breeding season on the east coast of Greenland.

Scientists found that the auks – one of the most abundant seabirds in the world – spend up to four weeks in a specific region of the Greenland Sea not doing much.

Their unusual idleness during this time suggests they use the area primarily to moult their flight feathers.

For the rest of the year, the birds tend to be on the go the whole time looking for food in the north Atlantic. But moulting renders them completely flightless. Indeed, in the same study scientists noticed that during their August and September moult, only two per cent of the birds were spotted flying, while 98 per cent sat on the sea surface.

It's likely they go to this region of the Atlantic not just to feed on tiny marine creatures called copepods, but also to escape predators on land.

'They're specialised plankton feeders, searching out the largest suitable zooplankton they can find: Arctic copepods. It's a wise choice, because these animals have high fat and therefore high energy content,' says Dr Anders Mosbech from Aarhus University, lead author of the study.

The likely reliance of so many birds on such a distinct region of the Greenland Sea means they're particularly vulnerable to changes in this part of the ocean. Scientists like Mosbech are particularly concerned about the effects of potential oil spills and climate change on the little auks.

'There's talk of opening up parts of the Greenland Sea for oil exploration, and an oil spill in a concentration area could seriously impact these birds. We're potentially talking about millions of birds going to a fairly distinct region,' says Mosbech.

Climate change is also expected to take its toll on little auks.

'The behaviour of these birds is adapted to the distribution of large Arctic copepods, which tend to be abundant in certain areas the Greenland Sea and north Atlantic, and depend on the climate. But copepods could move north as the sea warms up with the warming climate,' Mosbech explains.
Before this study, scientists knew very little about the auks outside their breeding season. But Mosbech says scientists need to understand their ecology so that they can manage the situation if oil spills and climate change does cause problems for the birds.

'The better we understand the distribution of the birds the better they can be protected in the planning of the oil activities,' he says.

Several million birds

Despite sightings of little auks in the north Atlantic, until now no one was quite sure where the several million birds from the Scoreby Sund Polynya and Kap Høegh colonies on the east coast of Greenland go once they leave their breeding grounds.

It's a very remote area and the seas in the Greenland Sea are rough and difficult to work in.
To find more about the movements of little auks once they've left Greenland, Mosbech and colleagues from the US, Greenland, UK and France decided to use tracking technology developed at the British Antarctic Survey.

They attached tiny devices called geolocators to 52 birds from the Kap Høegh colony during July 2007 and July 2008. Geolocators only weigh 1.4 grams, just one per cent of the weight an adult auk.
A year later, the researchers only managed to retrieve five loggers, because of either water damage, extreme temperatures or because they had difficulty finding the birds again.

'We had to rely on the birds returning to the same spot we captured them from a year earlier. But that's difficult, because there are millions of birds, and they sometimes change their nesting hole from year to year,' Mosbech explains.

After spending a few weeks in the Greenland Sea, Mosbech and his colleagues found that the birds head south to spend the winter off of Newfoundland.

He says the next thing is to find out exactly what they're feeding on and where they're getting their food from by studying stable isotopes.

'We also want to see where they're going to moult from other colonies across the Arctic,' says Mosbech.

Anders Mosbech, Kasper L. Johansen, Nikolaj I. Bech, Peter Lyngs, Ann M. A. Harding, Carsten Egevang, Richard A. Phillips and Jerome Fort, Inter-breeding movements of little auks Alle alle reveal a key post-breeding staging area in the Greenland Sea, Polar Biology, published online 18 August 2011, DOI: 10.1007/s00300-011-1064-4

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