These cute Adélie penguins (Pygoscelis adeliae) are actually having a bit of a spat. In the spring (October for them), the penguins form breeding colonies on rocky coasts with thousands of birds in a g.roup. Krill, a tiny crustacean, is the penguins' main food source, but krill populations are being affected by climate change and the Adélie penguin populations are decreasing (PDF) as a result. See more beautiful winning photos from Nature's Best 2012 contest.
“This primeval scene of an early morning squabble between this pair of penguins was amazing to witness. Under a moody sky, there seemed to be electricity in the air as they relentlessly fought back and forth for position and perhaps other reasons unknown to me. Lying on the snow waiting for them to approach, I was surprised to find them fighting nearly on top of me!” -- Nature's Best Photographer, Rod Strachan