Using high-resolution images taken using satellites, researchers analysed 44 colonies of emperor penguins around the coastline of Antarctica.

They found the total emperor penguin population could be put at 595,000, roughly double previous estimates of 270,000 to 350,000.

The discovery has been welcomed amid concerns that changes to levels of ice on the world's coldest continent could pose a threat to the species.

Peter Fretwell, who led the researchers at the British Antarctic Survey, said: “We are delighted to be able to locate and identify such a large number of emperor penguins. This is the first comprehensive census of a species taken from space.

"It gives us a bit more confidence not only that there are lots of emperor penguins out there but that we can actually keep track of them as well."

The technique used by the scientists allowed them to spot the black and white birds amongst the ice, rock and guano that litter the Antarctic landscape.

Emperor penguins breed in some of the most inhospitable and inaccessible conditions in the world, where temperatures can reach as low as -50C, making them difficult to study.

The satellite images, however, allowed the researchers to conduct the first detailed survey of the species. The study, which is published in the journal PLoS ONE, even identified seven colonies that had never been seen before.

A special technique known as pan-sharpening to increase the resolution of the satellite images allowed the researchers to differentiate between birds, shadows and penguin excrement, or guano.

The study marks the first time that researchers have counted the entire population of any species by satellite in a single season.

Dr Fretwell believes the same technique could also be use to tot up numbers of other wild animals that stand out clearly against their natural habitat, such as flamingos or reindeer.

Counting other types of penguins from space, however, may not be so easy. While emperors are large and contrast sharply against the white snow and ice on which they stand, other species are smaller and tend to breed on dark-coloured rock.

Michelle LaRue, from the University of Minnesota, said: “The implications of this study are far-reaching: we now have a cost-effective way to apply our methods to other poorly-understood species in the Antarctic, to strengthen ongoing field research, and to provide accurate information for international conservation efforts."

Conservation groups fear emperor penguins will be badly affected by climate change in the Antarctic as the colonies rely upon sea ice. Some research has suggested volumes of sea ice has been decreasing due to global warming.

More northerly colonies are thought to be particularly at risk. The new technique should allow scientists to monitor the impacts on the penguins in real time.

Dr Phil Trathan, a biologist at the British Antarctic Survey, said: “Current research suggests that emperor penguin colonies will be seriously affected by climate change.

"An accurate continent-wide census that can be easily repeated on a regular basis will help us monitor more accurately the impacts of future change on this iconic species.

"The effects of warming around Antarctica are regional and uneven. In the future we anticipate that the more southerly colonies should remain, making these important sites for further research and protection.”
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