The Arctic doesn't have penguins because it has puffins. The Antarctic doesn't have puffins because it has penguins. The two fill pretty much the same niche. If you've ever seen video footage of puffins feeding underwater, they swim almost as well as penguins. The main difference between the two, other than that puffins can still fly, is that penguins wear tuxedos while puffins wear clown suits.