The Black-throated Loon ( Gavia arctica ) , is a medium-sized member of the loon or diver family . The Black-throated Loon ( Gavia arctica ) is a migratory aquatic bird found in the northern hemisphere . The species is known as an Arctic Loon in North America and the Black-throated Diver in Eurasia , its current name is a compromise proposed by the International Ornithological Committee .