Observations of Rissa tridactyla were collected from the Baltic Sea area for HELCOM Red List species list. The HELCOM Red List of Baltic Sea species in danger of becoming extinct (2013) is the first threat assessment for Baltic Sea species that covers all marine mammals, fish, birds, macrophytes (aquatic plants), and benthic invertebrates, and follows the Red List criteria of the International Union for Conservation of Nature (IUCN). Almost 2800 species were considered in the Red List assessment and about 1750 were evaluated according to the IUCN Red List criteria. Rissa tridactyla has different populations for breeding and wintering seasons. Breeding population has been placed to the Red List category of Endangered (EN) species, whereas wintering population belongs to the category of Vulnerable (VU) species. The map shows the species range only during breeding season.