Gray seabird shaped like a football. Breeding plumage shows white belly and thin white eyebrow and mustache. Distinctive stout orange bill with pale vertical protrusion at base. Nonbreeding birds have a plainer face and lack "horn" on bill; juveniles have gray bill. Longer bill than other auklets with a flatter head. Breeds on offshore islands; otherwise found at sea, usually alone. Dives underwater for fish.