An auk is a bird of the family Alcidae in the order Charadriiformes.

However, some of them are now globally extinct, like the Great Auk ( Pinguinus impennis ), the European Wild Horse ( Equus ferus ) and the Aurochs ( Bos primigenius primigenius ).

You can do the same thing, as the costs come down, for the Carolina parakeet, for the great auk, for the heath hen, for the ivory billed woodpecker, for the Eskimo curlew, for the Caribbean monk seal, for the woolly mammoth.