Using satellite mapping with resolution high enough to distinguish ice shadows from penguin poo, an international team has carried out what they say is an unprecedented penguin census from the heavens over the past three years.

The good news was that the team found the Antarctic emperor penguin population numbered about 595,000, nearly double previous estimates.

But the bad news was that some colonies have disappeared altogether due to changing weather patterns and the long-term future of the birds is far from assured.

"Yes, this is the first comprehensive census of a species taken from space, absolutely," said Barbara Wienecke, a sea bird ecologist with the Australian Antarctic Division (AAD) who spoke with Reuters by phone from the Aurora Australis research vessel.

Previous counts have been inaccurate due to rough terrain that made some colonies inaccessible and frigid temperatures that can plummet to - 50 degrees Celsius (- 58 Fahrenheit).

This time the group, a collaboration between the AAD, the British Antarctic Survey, the University of Minnesota/National Science Foundation and Scripps Institution of Oceanography, used aerial photography to calibrate their analysis of counts taken on the ground.

Emperor penguins, with their distinctive black and white plumage, stand out against the snow. That means colonies are clearly visible on satellite images, the group found. Their results are published in the journal PLoS ONE.

The technique also has the advantage of having no negative impact on the sensitive Antarctic environment or the birds.

"Most of the time it is impossible to take into consideration every single colony, but now we are in a position that we can actually compare how the sea ice environment changes and hopefully continue to monitor the population - and see which ones may or may not be decreasing in size," Wienecke said.

Previous censuses using more traditional counting methods came up with estimates of 270,000 to 350,000 birds.

While the greater number of penguins is encouraging, changing weather patterns mean their survival is far from assured. The larger population may also pressure the numbers of krill in the oceans, an essential food for the penguins.

Warming oceans observed by the research team can also have an impact. Of particular concern is what happens with "long fast ice" - ice that is attached to the continent and forms a continuous flat area of frozen ocean.

Such ice is where most of the penguin colonies are found, its flat surface essential for the male penguins who incubate each mating pair's single egg on their feet.

"Things change very quickly, so we can't take comfort in having half a million birds at the moment," Wienecke said.

"If the fast ice changes, the birds can end up in a lot of strife very, very quickly."

(Editing by Elaine Lies and Paul Tait)

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