Almost total migrant to northern breeding areas, where rarely recorded November–January; majority perform long journeys, including regular post-breeding migration from Europe to South America by juveniles and adults. Southward passage begins July, juveniles following September; return movements to breeding areas late February to early April, with influx of older immatures about May. Details of movements mainly from ringing in Wales. Breeding birds make feeding movements of some days duration, but no confirmation yet for theory that these reach Bay of Biscay, though some suggestion from recoveries that may do so in pre-laying exodus; could not do so after hatching of young when absences too short. Large winter concentration, especially October–December, off east coast of South America, 10°S-40°S, but most recoveries between 20°S-30°S. Dearth of recoveries anywhere between January and early February suggests return by different route, possible counter-clockwise movement in South Atlantic, for which some support from recent sightings of small numbers off southern Africa in January–February. Immatures do not come ashore at colonies in 2nd calendar year but degree of return to European seas uncertain. Small numbers occur off New England-Newfoundland area (vagrant to south Greenland) late March to mid-September; the few recoveries indicate these include high proportion of 2nd calendar year birds which may have migrated north up west Atlantic from winter quarters. Rare in North Sea; has occurred as vagrant in several European countries with exceptional records far inland. In Britain, a few juveniles found inland after gales in most autumns. Atypical recoveries of Welsh-ringed birds (mostly recently fledged) in Norway and Denmark (September), Mediterranean France (February), Canary Islands (September), Equatorial Guinea (September), Ghana (October), Trinidad and Grenada (November), and South Australia (November). One of unknown origin found New Zealand June 1972. Nominate race also breeds subtropical North Atlantic islands; movements unknown, but reported absent from Madeira November–February.
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