Predation by a small but growing number of skuas Catharacta skua (170 pairs) may be partly responsible.    From Wordnik.com.  [St Kilda (Hirta) National Nature Reserve, United Kingdom] Reference

Only the marauding subantarctic skua Catharacta antarctica feeds on the island, mostly on spectacled petrels.    From Wordnik.com.  [Gough Island Wildlife Reserve, United Kingdom] Reference

American sheathbill (Chionis alba); south polar skua (Catharacta maccormicki); brown skua (Catharacta lonnbergi); southern black-backed gull (Larus dominicanus); and.    From Wordnik.com.  [Antarctic Peninsula] Reference

Le Corre suggests that the occurrence of the white-tailed brown morph at Europa may act as a defensive camouflage against kleptoparasitism (a behavior of stealing another bird's catch) by great frigatebirds (Fregata minor) and brown skuas (Catharacta antarctica).    From Wordnik.com.  [Ile Europa and Bassas da India xeric scrub] Reference

However, calling is a costly activity in some petrel species since avian predators, such as skuas Catharacta skua lönnbergi, use calls to localize their petrel prey.    From Wordnik.com.  [PLoS ONE Alerts: New Articles] Reference

Other residents of the islands are sooty albatross (Phoebetria fusca) (240 pairs), remnant populations of soft-plumaged petrel (Pterodroma mollis) and grey petrel (Procellaria cinera), antarctic tern (Sterna vittata tristanensis), brown skua (Catharacta lonnbergi), and common waxbill (Estrilda astrild) (introduced 1977-1985).    From Wordnik.com.  [Amsterdam and Saint-Paul Islands temperate grasslands] Reference

Great skua (Catharacta skua) III.    From Wordnik.com.  [Management and conservation of marine mammals and seabirds in the Arctic] Reference