Skua

Skuas are a group of birds of the genus "Stercorarius". They live near the ocean and have an aggressive lifestyle. They chase other birds to steal their catches, and they do fight, kill and eat other seabirds. Their victims include gulls, terns, puffins, and penguins. 
Skuas nest on the ground in temperate and arctic regions. They travel a long way to migrate, and have even been seen at the South Pole.