Named for the peculiar vertical horn at the base of its bill, this unique Alcid is in its own monotypic genus. This is a burrow nesting species and the largest Alcid to visit its nest only during the night. Unlike other nocturnal Alcids, this species carries food to the nest externally, with multiple prey items held in its bill. Smaller Alcids carry food internally in their crop. This species disappeared as a breeder on the Farallons in the late 19th century but returned to breed there in the early 1970s. As its range continues to expand southward, there are now 28 colonies in California as far south as San Miguel Island.
