BirdLife International: Stercorarius skuaIUCN Red List of Threatened Species. Version 2013.2. 2012. International Union for Conservation of Nature, IUCN, Iucnredlist.org. Viitattu 29.5.2014. (englanniksi)
Catharacta skua (Great Skua)The IUCN Red List of Threatened Species. International Union for Conservation of Nature and Natural Resources. ”The breeding population, which is confined to Europe, is estimated at 16,300-17,200 pairs, which roughly equates to 30,000-34,999 mature individuals (BirdLife International 2015).” Viitattu 23.2.2025. (englanniksi)
Catharacta skua (Great Skua) (pdf) The IUCN Red List of Threatened Species. Supplementary information. International Union for Conservation of Nature and Natural Resources & BirdLife International. Viitattu 23.2.2025. (englanniksi)