page_title: European storm petrel
section_title: Predators and parasites
hierarchical_section_title: European storm petrel / Predators and parasites
caption_attribution_description: English: light morph adult, wild Eleonora's Falcon at Cap Formentor on Mallorca, Spain Europe
context_page_description: The European storm petrel, British storm petrel, or just storm petrel is a seabird in the northern storm petrel family, Hydrobatidae. It is the only member of the genus Hydrobates. The small, square-tailed bird is entirely black except for a broad, white rump and a white band on the under wings, and it has a fluttering, bat-like flight. The large majority of the population breeds on islands off the coasts of Europe, with the greatest numbers in the Faroe Islands, United Kingdom, Ireland, and Iceland. The Mediterranean population is a separate subspecies, but is inseparable at sea from its Atlantic relatives; its strongholds are Filfla Island, Sicily, and the Balearic Islands.
  The storm petrel nests in crevices and burrows, sometimes shared with other seabirds or rabbits, and lays a single white egg, usually on bare soil. The adults share the lengthy incubation and both feed the chick, which is not normally brooded after the first week. This bird is strongly migratory, spending the Northern Hemisphere winter mainly off the coasts of South Africa and Namibia, with some birds stopping in the seas adjoining West Africa, and a few remaining near their Mediterranean breeding islands.
context_section_description: Adults and young are vulnerable to predation at the breeding colonies, their only defence being to spit oil. Petrels cannot breed on islands where rats have been introduced, and feral cats frequently kill these birds on Foula in the Shetland Islands. The American mink, a non-native species in Europe, is a strong swimmer, and can colonise islands up to 2 km (2,200 yd) from the mainland. Natural predators of petrels and other seabirds include skuas and large gulls. The yellow-legged gull is a particular problem in the Mediterranean, and great skuas were estimated to kill 7,500 petrels a year on St Kilda, an unsustainable number. Some great black-backed gulls on the Atlantic islands specialise in taking seabird chicks at night, and peregrine falcons hunt adults at sea. Localised predators include Eleonora's falcon on the Columbretes Islands and the nocturnal barn owl on the Balearics; a few owls can wipe out a colony. The little owl is also a predator of both adults and young where it occurs.
  Feather mites of at least two species have been found on the storm petrel, with Halipeurus pelagicus occurring at much higher densities than Philoceanus robertsi. The flea Xenopsylla gratiosa and dermanyssid mites are commonly found, with lower numbers of ticks. These blood-sucking parasites slow the growth rate of nestlings and may affect their survival rate.
  Storm petrels seem to be largely free of blood parasites, even when in close proximity to carrier species such as the yellow-legged gull. It has been suggested that seabird species with long incubation periods and long lives have well-developed immune systems that prevent serious blood parasitism.
caption: The Eleanora's falcon is a local predator on some Mediterranean islands
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