Journal of Ornithology

, Volume 147, Issue 3, pp 405–413 | Cite as

Nocturnal foraging by great skuas Stercorarius skua: implications for conservation of storm-petrel populations

  • Stephen C. VotierEmail author
  • Jonathan E. Crane
  • Stuart Bearhop
  • Ana de León
  • Claire A. McSorley
  • Eduardo Mínguez
  • Ian P. Mitchell
  • Matthew Parsons
  • Richard A. Phillips
  • Robert W. Furness
Original Article


At St Kilda, Outer Hebrides, a large colony of great skuas Stercorarius skua feed extensively on one of the largest colonies of Leach’s storm-petrels Oceanodroma leucorhoa in Europe, but little is known about the dynamics of this predator–prey system. Recently published population estimates of storm-petrels make it possible to estimate the impact of skua predation for the first time. Although skuas in the southern hemisphere catch petrels attending breeding colonies at night, it is not known whether congeners in the northern hemisphere also forage during the hours of darkness. We found (using radio-transmitters) that skuas regularly forage at night and (using light intensifying equipment) observed them catching storm-petrels at night. However, skuas also foraged during daylight hours, and it is unknown whether they might also catch storm-petrels at sea. Data on diet composition reveals that the proportion of storm-petrels in skua diet declined between 1996 and 1997, but remained constant thereafter. Although a large proportion of the storm-petrel prey is likely to consist of non-breeders, numbers consumed suggest that breeders and an unknown quantity of transients may also been eaten. The numbers of storm-petrels eaten are not sustainable and may result in substantial long-term population declines. Under current conditions, maintenance of large populations of both Leach’s storm-petrels and great skuas at St Kilda appears to be mutually exclusive.


Stercorarius skua Oceanodroma leucorhoa Predator–prey dynamics Conservation Foraging. 



We should like to thank Jill Haydon, Natalie McCall and Susan Bain from NTS Scotland, Adrian Plant for help in the field and the workers at QINETIQ who were all so helpful. Sascha Hooker kindly loaned us the Televilt remote sensing system. This research complied with all necessary licences and permissions and was funded by EC project DISBIRD and an NERC Fellowship to SB.


  1. Adams NJ (1982) Subantarctic skua prey remains as an aid for rapidly assessing the status of burrowing petrels at Prince Edward Island. Cormorant 10:97–102Google Scholar
  2. Bearhop S, Thompson DR, Phillips RA, Waldron S, Hamer KC, Gray CM, Votier SC, Ross BP, Furness RW (2001) Annual variation in great skua diets: the importance of commercial fisheries and predation on seabirds revealed by combining dietary analyses. Condor 103:802–809CrossRefGoogle Scholar
  3. Catry P, Furness RW (1999) The influence of adult age on territorial attendance by breeding great skuas Catharacta skua: an experimental study. J Avian Biol 30:399–406CrossRefGoogle Scholar
  4. Cramp S, Simmons KEL (1977) Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic, vol. 1. Oxford University Press, OxfordGoogle Scholar
  5. del Hoyo J, Elliot A, Sargatal J (1996) Handbook of the Birds of the World, vol 1. Hoatzin to Auks. Lynx Edicions, BarcelonaGoogle Scholar
  6. Darling FF (1938) Bird flocks and the breeding cycle. Cambridge University Press CambridgeGoogle Scholar
  7. Fowler J (2002) European Storm-petrel Hydrobates pelagicus. In: Wernham C, Toms M, Marchant J, Clark J, Siriwardena G, Baillie S (eds) The migration atlas: movements of the birds of Britain and Ireland. T & A D Poyser, London, pp 124–127Google Scholar
  8. Furness RW (1987) The Skuas. Poyser Press, Calton, StaffsGoogle Scholar
  9. Love JA (1976) Identification from measurements of small petrel remains in gull and skua pellets. Bird Study 23:162Google Scholar
  10. McNeil R, Drapeau P, Pierotti R (1993) Nocturniality in colonial Waterbirds: occurrence, special adaptations and suspected benefits. Current Ornithology 10:187–246Google Scholar
  11. Mitchell PI, Newton SF, Ratcliffe N, Dunn TE (2004) Seabird populations of Britain and Ireland. T & A D Poyser, LondonGoogle Scholar
  12. Mougeot F, Bretagnolle V (2000) Predation as a cost of sexual communication in nocturnal seabirds: an experimental approach using acoustic signals. Anim Behav 60:647–656CrossRefPubMedGoogle Scholar
  13. Mougeot F, Genevois F, Bretagnolle V (1998) Predation on burrowing petrels by the brown skua Catharacta skua lonnbergi at Mayes Island, Kerguelen. J Zool (Lond) 244:429–438Google Scholar
  14. Ollason JC, Dunnet GM (1978) Age, experience and other factors affecting the breeding success of the fulmar, Fulmarus glacialis, in Orkney. J Anim Ecol 47:961–976CrossRefGoogle Scholar
  15. Phillips RA, Catry P, Thompson DR, Hamer KC, Furness RW (1997) Inter-colony variation in diet and reproductive performance of great skuas Catharacta skua. Mar Ecol Prog Ser 152:285–293CrossRefGoogle Scholar
  16. Phillips RA, Bearhop S, Hamer KC, Thompson DR (1999a) Rapid population growth of great skuas at St Kilda: implications for management and conservation. Bird Study 46:174–183CrossRefGoogle Scholar
  17. Phillips RA, Thompson DR, Hamer KC (1999b) The impact of great skua predation on seabird populations at St Kilda: a bioenergetics model. J Appl Ecol 36:218–232CrossRefGoogle Scholar
  18. Phillips RA, Phalan B, Forster IP (2004) Diet and long-term changes in population size and productivity of brown skuas Catharacta antarctica lonnbergi at Bird Island, South Georgia. Polar Biol 27:555–561CrossRefGoogle Scholar
  19. Pierotti R, Annett CA (1991) Diet choice in the herring gull: constraints imposed by reproductive and ecological factors. Ecology 72:319–328CrossRefGoogle Scholar
  20. Pollock CM, Mavor R, Weir CR, Reid A, White RW, Tasker ML, Webb A, Reid JB (2000) The distribution of seabirds and marine mammals in the Atlantic Frontier, north and west of Scotland. Joint Nature Conservation Committee, PeterboroughGoogle Scholar
  21. Reinhardt K, Hahn S, Peter H-U, Wemhoff H (2000) A review of the diets of Southern Hemisphere skuas. Mar Ornithol 28:7–19Google Scholar
  22. Ryan PG, Moloney CL (1991) Prey selection and temporal variation in the diet of Subantarctic skuas at Inaccessible Island, Tristan da Cunha. Ostrich 62:52–58Google Scholar
  23. Tasker ML (2002) Leach’s Storm-petrel Oceanodroma leuchoroa. In: Wernham C, Toms M, Marchant J, Clark J, Siriwardena G, Baillie S (eds) The migration atlas: movements of the birds of Britain and Ireland. T & A D Poyser, London, pp 128–129Google Scholar
  24. Votier SC, Bearhop S, MacCormick A, Ratcliffe N, Furness RW (2003) Assessing the diet of great skuas using five different techniques. Polar Biol 26:20–26Google Scholar
  25. Votier SC, Bearhop S, Ratcliffe N, Furness RW (2001) Pellets as indicators of diet in great skuas. Bird Study 48:373–376Google Scholar
  26. Votier SC, Bearhop S, Ratcliffe N, Furness RW (2004a) Reproductive consequences for Great Skuas specializing as seabird predators. Condor 106:275–287CrossRefGoogle Scholar
  27. Votier SC, Bearhop S, Ratcliffe N, Phillips RA, Furness RW (2004b) Predation by great skuas at a large seabird colony. J Appl Ecol 41:1117–1128CrossRefGoogle Scholar
  28. Votier SC, Furness RW, Bearhop S, Crane JE, Caldow RWG, Catry P, Ensor K, Hamer KC, Hudson AV, Kalmbach E, Klomp NI, Pfeiffer S, Phillips RA, Prieto I, Thompson DR (2004c) Changes in fisheries discard rates and seabird communities. Nature 427:727–730CrossRefPubMedGoogle Scholar
  29. Warham J (1996) The behaviour, population biology and physiology of the petrels. Academic Press, LondonGoogle Scholar
  30. Watanuki Y (1986) Moonlight avoidance behaviour in Leach’s storm-petrels as a defence against slaty-backed gulls. Auk 103:14–22Google Scholar

Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2005

Authors and Affiliations

  • Stephen C. Votier
    • 1
    Email author
  • Jonathan E. Crane
    • 2
  • Stuart Bearhop
    • 3
  • Ana de León
    • 2
  • Claire A. McSorley
    • 4
  • Eduardo Mínguez
    • 5
  • Ian P. Mitchell
    • 4
  • Matthew Parsons
    • 4
  • Richard A. Phillips
    • 6
  • Robert W. Furness
    • 2
  1. 1.Marine Biology and Ecology Research Centre, School of Biological SciencesUniversity of PlymouthPlymouthUnited Kingdom
  2. 2.Institute of Biomedical and Life Sciences, Graham Kerr BuildingUniversity of GlasgowGlasgowUnited Kingdom
  3. 3.School of Biology and Biochemistry, Medical Biology CentreQueens UniversityBelfastNorthern Ireland
  4. 4.Joint Nature Conservation CommitteeDunnet HouseAberdeenUnited Kingdom
  5. 5.Departamento de Biología Aplicada, Área de EcologíaUniversidad Miguel Hernández. Avda. de la UniversidadElcheSpain
  6. 6.British Antarctic SurveyNatural Environment Research CouncilCambridgeUnited Kingdom

Personalised recommendations