In the summer the great auk went to rocky islands to breed in large colonies. Breeding islands were remote and mostly low-lying, and usually quite close to rich fishing grounds.
The great auk only ever came ashore in rocky offshore islands to breed.
Each pair laid a single egg on bare rock.
The great auk foraged in shallow waters eating fish, crabs and plankton.
They migrated south in the winter, and bones have been found as far south as Florida and Gibraltar.