Which specific species undertakes some of the longest migrations of any animal, traveling pole-to-pole?

Answer

South Polar Skua

Satellite tracking data reveals that the South Polar Skua undertakes some of the longest migrations globally, traveling between its Antarctic breeding grounds and the North Pacific or North Atlantic.

Which specific species undertakes some of the longest migrations of any animal, traveling pole-to-pole?
taxonomybirdanimalclassificationSkua