Recent satellite observations show birds adapting to changes in sea ice
By Bob Berwyn
FRISCO — Emperor penguins living at the edge of their range may be able to find new breeding grounds as their sea-ice breeding habitat dwindles in coming decades.
Recent satellite monitoring shows that the Antarctic birds moved from their traditional sea-ice breeding grounds during years when the thin layer of ice (sea ice) formed later than usual to the much thicker floating ice shelves that surround the continent.
“When they turn up to breed, there needs to be a solid blanket of sea ice,” said British Antarctic Survey researcher Peter Frewell, lead author of the paper published this week in the online journal, PLOS ONE. The research team also included scientists from the Australian Antarctic Division and the Scripps Institution of Oceanography at UC San Diego in California.
“These charismatic birds tend to breed on the sea ice because it gives them relatively easy access to waters where they hunt for food,” Frewell said. The ongoing satellite monitoring showed, for examplee, that one colony was able to find suitable sea ice habitat from 2008 through 2010.
But in 2011 and 2012, the ice didn’t form until a month after the breeding season began. During those years the birds adapted by moved up onto the neighboring floating ice shelf to raise their young.
“What’s particularly surprising is that climbing up the sides of a floating ice shelf – which at this site can be up to 30 metres high – is a very difficult maneuver for emperor penguins. Whilst they are very agile swimmers they have often been thought of as clumsy out of the water,” Frewell said.
So far, there haven’t been direct observation of the penguins climbing up the steep ledges of the ice shelves, but the researcher suspect that the birds are using terrain features like gullies to gain access. In some cases, the treks are quite long, raising questions about how much energy the birds are using to reach those ice shelf breeding grounds, Frewell said.
The emperor penguins’ reliance on sea ice as a breeding platform, coupled with recent concern about changing patterns of sea ice, has led to the species being designated as ‘near threatened’ by the IUCN red list. The discovery suggests the species may be capable of adapting their behavior, but the researchers aren’t completely sure if this is a recent change.
“They may have been doing this since time immemorial,” Frewell said, adding that more long-term observations may help further unravel the mystery.
“These new findings are an important step forward in helping us understand what the future may hold for these animals, however, we cannot assume that this behavior is widespread in other penguin populations,” said Barbara Wienecke, of the Australian Antarctic Division.
The ability of these four colonies to relocate to a different environment — from sea ice to ice shelf — in order to cope with local circumstances, was totally unexpected. We have yet to discover whether or not other species may also be adapting to changing environmental conditions.”
Gerald Kooyman, of the Scripps Institution added: “Without satellite imagery these moves onto shelf ice would not have been detected. It is likely that there are other nuances of the emperor penguin environment that will be detected sooner through their behaviour than by more conventional means of measuring environmental changes.”