Adelie penguins surfacing for air as they swim, ca.2008. Photo by Chris Linder, Woods Hole Oceanographic Institution. 
"Thick fog most of the day," wrote Amundsen. "In the afternoon, saw a large flock of penguins (small) in the sea. They were heading due South -- Both fog and penguins are distinct signs that we are not far from the ice." 
 Woods Hole Oceanographic Institution. Used with permission.
 Roald Amundsen, diary, 27 December, 1910, quoted by Roland Huntford in The Amundsen Photographs (London : Hodder & Stoughton, c1987), p.71.