Polar Biology

, Volume 42, Issue 2, pp 423–432 | Cite as

Surveys reveal increasing and globally important populations of south polar skuas and Antarctic shags in Ryder Bay (Antarctic Peninsula)

  • Richard A. PhillipsEmail author
  • Janet R. D. Silk
  • Alison Massey
  • Kevin A. Hughes
Original Paper


Despite their importance in ecosystems, population sizes and trends are unknown for many seabirds, including in the Antarctic. Here we report on the first comprehensive survey of south polar skuas Stercorarius maccormicki and Antarctic shags Leucocarbo bransfieldensis in Ryder Bay, and collate previous count data. In austral summer 2017/18, totals of 259 skuas at club sites and 978 occupied skua territories were counted in 2.3 km2 of suitable habitat at Rothera Point and adjacent islands. Based on the mean nearest neighbour distance (23.2 m), skua nest densities were comparable with colonies elsewhere. Long-term monitoring of skuas at Rothera Point indicated considerable annual variation and overall increases of 1.9 and 1.3% per annum, respectively, in breeding pairs from 1975/76 to 2017/18, and occupied territories from 1988/89 to 2017/18. In total, 405 pairs of Antarctic shags bred at two known and one newly discovered colony in 2017/18. Previous counts at the two known colonies indicated substantial annual variation and increases of 5.5 and 3.3% per annum, respectively, from 1985/86 to 2017/18 and 1989/90 to 2017/18. Factors leading to overall increases in both species, and the intermittent seasons of near-complete failure to breed, are unclear, but likely to reflect impacts of environmental change on their marine prey or sea ice. The breeding populations of south polar skuas and Antarctic shags in Ryder Bay represent 10.3 and 3.5%, respectively, of revised global estimates of 9500 and 11,684 breeding pairs. We recommend that the breeding colonies be included as important bird areas (IBAs) and within the Antarctic Specially Protected Area (ASPA) system, and provision made to conserve foraging areas at sea.


Antarctic Peninsula Blue-eyed shag Imperial shag Important bird area Long-term monitoring Marguerite Bay Population trends 



We are very grateful to the many field assistants for help with monitoring of skuas at Rothera Point over many years, to Ali Rose for help with the skua census in 2018, to Peter Fretwell for photographing and counting the shag colony at the Mikkelsen Islands and to Sally Poncet for providing unpublished counts of shag nests. The boating officers and crew at Rothera diligently transported us to the Ryder Bay islands. We are grateful to Johannes Krietsch, Jan Esefeld and an anonymous referee for their comments on the manuscript. This study represents a contribution to the Ecosystems Component of the British Antarctic Survey Polar Science for Planet Earth Programme and the Environment Office Long-term Monitoring and Survey project (EO-LTMS), funded by the Natural Environment Research Council.

Compliance with ethical standards

Conflict of interest

The authors are not aware of any conflicts of interest with regard to this study.


  1. Ainley DG, Ribic CA, Wood RC (1990) A demographic study of the South Polar Skua Catharacta maccormicki at Cape Crozier. J Anim Ecol 59:1–20CrossRefGoogle Scholar
  2. Black C, Rey AR, Hart T (2017) Peeking into the bleak midwinter: Investigating nonbreeding strategies of Gentoo Penguins using a camera network. Auk 134:520–529CrossRefGoogle Scholar
  3. Borowicz A, McDowall P, Youngflesh C, Sayre-McCord T, Clucas G, Herman R, Forrest S, Rider M, Schwaller M, Hart T (2018) Multi-modal survey of Adélie penguin mega-colonies reveals the Danger Islands as a seabird hotspot. Sci Rep 8:3926CrossRefGoogle Scholar
  4. Bracegirdle TJ, Connolley WM, Turner J (2008) Antarctic climate change over the twenty first century. J Geophys Res Atmos 113:D03103CrossRefGoogle Scholar
  5. Brooke ML (2004) The food consumption of the world's seabirds. Proc R Soc Lond B 271:S246–S248Google Scholar
  6. Carneiro AP, Manica A, Phillips RA (2016) Long-term changes in population size, distribution and productivity of skuas (Stercorarius spp.) at Signy Island, South Orkney Islands. Polar Biol 39:617–625CrossRefGoogle Scholar
  7. Casanovas P, Naveen R, Forrest S, Poncet J, Lynch HJ (2015) A comprehensive coastal seabird survey maps out the front lines of ecological change on the western Antarctic Peninsula. Polar Biol 38:927–940CrossRefGoogle Scholar
  8. Casaux R, Barrera-Oro E (2006) Shags in Antarctica: their feeding behaviour and ecological role in the marine food web. Antarct Sci 18:3–14CrossRefGoogle Scholar
  9. Catry P, Phillips RA, Hamer KC, Ratcliffe N, Furness RW (1998) The incidence of nonbreeding by adult great skuas and parasitic jaegers from Foula, Shetland. Condor 100:448–455CrossRefGoogle Scholar
  10. Che-Castaldo C, Jenouvrier S, Youngflesh C, Shoemaker KT, Humphries G, McDowall P, Landrum L, Holland MM, Li Y, Ji R, Lynch HJ (2017) Pan-Antarctic analysis aggregating spatial estimates of Adélie penguin abundance reveals robust dynamics despite stochastic noise. Nat Commun 8:832CrossRefGoogle Scholar
  11. Constable AJ, de la Mare WK, Agnew DJ, Everson I, Miller D (2000) Managing fisheries to conserve the Antarctic marine ecosystem: practical implementation of the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). ICES J Mar Sci 57:778–791CrossRefGoogle Scholar
  12. Croxall JP, Butchart SHM, Lascelles B, Stattersfield AJ, Sullivan B, Symes A, Taylor P (2012) Seabird conservation status, threats and priority actions: a global assessment. Bird Conserv Int 22:1–34CrossRefGoogle Scholar
  13. Einoder LD (2009) A review of the use of seabirds as indicators in fisheries and ecosystem management. Fish Res 95:6–13CrossRefGoogle Scholar
  14. Forcada J, Trathan PN, Murphy EC (2008) Life history buffering in Antarctic mammals and birds against changing patterns of climate and environmental variation. Glob Change Biol 14:2473–2488Google Scholar
  15. Fraser WR, Hofmann EE (2003) A predator’s perspective on causal links between climate change, physical forcing and ecosystem response. Mar Ecol Prog Ser 265:1–15CrossRefGoogle Scholar
  16. Fretwell PT, Phillips RA, Brooke MDL, Fleming AH, McArthur A (2015) Using the unique spectral signature of guano to identify unknown seabird colonies. Remote Sens Environ 156:448–456CrossRefGoogle Scholar
  17. Fretwell PT, Scofield P, Phillips RA (2017) Using super-high resolution satellite imagery to census threatened albatrosses. Ibis 159:481–490CrossRefGoogle Scholar
  18. Furness RW (1987) The Skuas. T. & A.D, Poyser, Calton, StaffordshireGoogle Scholar
  19. Gonzalez-Zevallos D, Santos MM, Rombolá EF, Juáres MA, Coria NR (2013) Abundance and breeding distribution of seabirds in the northern part of the Danco Coast, Antarctic Peninsula. Polar Res 32:11133CrossRefGoogle Scholar
  20. Graña Grilli M (2014) Decline in numbers of Antarctic skuas breeding at Potter Peninsula, King George Island, Antarctica. Mar Ornithol 42:161–162Google Scholar
  21. Grant SM, Convey P, Hughes KA, Phillips RA, Trathan PN (2012) Conservation and management of Antarctic ecosystems. In: Rogers AD, Murphy EJ, Clarke A, Johnston NM (eds) Antarctic ecosystems: an extreme environment in a changing world. Wiley, London, pp 492–525CrossRefGoogle Scholar
  22. Hahn S, Ritz M, Reinhardt K (2008) Marine foraging and annual fish consumption of a south polar skua population in the maritime Antarctic. Polar Biol 31:959–969CrossRefGoogle Scholar
  23. Harris CM, Lorenz K, Fishpool LDC, Lascelles B, Cooper J, Coria NR, Croxall JP, Emmerson LM, Fijn RC, Fraser WL, Jouventin P, LaRue MA, Le Maho Y, Lynch HJ, Naveen R, Patterson-Fraser DL, Peter H-U, Poncet S, Phillips RA, Southwell CJ, van Franeker JA, Weimerskirch H, Wienecke B, Woehler EJ (2015) Important bird areas in Antarctica 2015. BirdLife International and Environmental Research & Assessment Ltd., CambridgeGoogle Scholar
  24. Hemmings AD (1990) Human impacts and ecological constraints on skuas. In: Kerry KR, Hempel G (eds) Antarctic ecosytems: ecological change and conservation. Springer, Berlin, pp 224–230CrossRefGoogle Scholar
  25. Higgins PJ, Davies SJJF (1996) Handbook of Australian, New Zealand and Antarctic birds. Vol 3. Snipe to pigeons. Oxford University Press, MelbourneGoogle Scholar
  26. Hinke JT, Salwicka K, Trivelpiece SG, Watters GM, Trivelpiece WZ (2007) Divergent responses of Pygoscelis penguins reveal a common environmental driver. Oecologia 153:845–855CrossRefGoogle Scholar
  27. Holland PR, Kwok R (2012) Wind-driven trends in Antarctic sea-ice drift. Nat Geosci 5:872–875CrossRefGoogle Scholar
  28. Hughes K, Pertierra L, Walton D (2013) Area protection in Antarctica: How can conservation and scientific research goals be managed compatibly? Environ Sci Policy 31:120–132CrossRefGoogle Scholar
  29. Kennedy M, Spencer HG (2014) Classification of the cormorants of the world. Mol Phylogenet Evol 79:249–257CrossRefGoogle Scholar
  30. Krietsch J, Esefeld J, Braun C, Lisovski S, Peter H-U (2016) Long-term dataset reveals declines in breeding success and high fluctuations in the number of breeding pairs in two skua species breeding on King George Island. Polar Biol 39:573–582CrossRefGoogle Scholar
  31. Lynch HJ, Schwaller MR (2014) Mapping the abundance and distribution of Adélie Penguins using Landsat-7: first steps towards an integrated multi-sensor pipeline for tracking populations at the continental scale. PLoS ONE 9:e113301CrossRefGoogle Scholar
  32. Lynch HJ, Naveen R, Fagan WF (2008) Censuses of penguin, blue-eyed shag Phalacrocorax atriceps and southern giant petrel Macronectes giganteus populations on the Antarctic Peninsula, 2001–2007. Mar Ornithol 36:83–97Google Scholar
  33. Lynch HJ, Naveen R, Trathan PN, Fagan WF (2012) Spatially integrated assessment reveals widespread changes in penguin populations on the Antarctic Peninsula. Ecology 93:1367–1377CrossRefGoogle Scholar
  34. Milius N (2000) The birds of Rothera, Adelaide Island, Antarctic Peninsula. Mar Ornithol 28:63–67Google Scholar
  35. Olivier F, van Franeker JA, Creuwels JCS, Woehler EJ (2005) Variations of snow petrel breeding success in relation to sea-ice extent: detecting local response to large-scale processes? Polar Biol 28:687–699CrossRefGoogle Scholar
  36. Parmalee DF, Bernstein NP, Neilson DR (1978) Impact of unfavorable ice conditions on bird productivity at Palmer Station during the 1977–78 field season. Antarct J US 13:146–147Google Scholar
  37. Pezzo F, Olmastroni S, Corsolini S, Focardi S (2001) Factors affecting the breeding success of the south polar skua Catharacta maccormicki at Edmonson Point, Victoria Land, Antarctica. Polar Biol 24:389–393CrossRefGoogle Scholar
  38. Phillips RA, Bearhop S, Hamer KC, Thompson D (1999a) Rapid population growth of Great Skuas Catharacta skua at St Kilda: implications for management and conservation. Bird Study 46:174–183CrossRefGoogle Scholar
  39. 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
  40. 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
  41. Phillips RA, Gales R, Baker G, Double M, Favero M, Quintana F, Tasker ML, Weimerskirch H, Uhart M, Wolfaardt A (2016) The conservation status and priorities for albatrosses and large petrels. Biol Conserv 201:169–183CrossRefGoogle Scholar
  42. Pietz PJ (1987) Feeding and nesting ecology of sympatric south polar and brown skuas. Auk 104:617–627Google Scholar
  43. Ratcliffe N, Guihen D, Robst J, Crofts S, Stanworth A, Enderlein P (2015) A protocol for the aerial survey of penguin colonies using UAVs. J Unmanned Veh Syst 3:95–101CrossRefGoogle Scholar
  44. Reinhardt K, Hahn S, Peter H-U, Wemhof H (2000) A review of the diets of Southern Hemisphere skuas. Mar Ornithol 28:7–19Google Scholar
  45. Ryan P, Whittington P, Crawford RJ (2009) A tale of two islands: contrasting fortunes for subantarctic skuas at the Prince Edward Islands. Afr J Mar Sci 31:431–437CrossRefGoogle Scholar
  46. Schrimpf M, Naveen R, Lynch HJ (2018) Population status of the Antarctic shag Phalacrocorax (atriceps) bransfieldensis. Antarct Sci 30:151–159CrossRefGoogle Scholar
  47. Shaw JD, Terauds A, Riddle MJ, Possingham HP, Chown SL (2014) Antarctica’s protected areas are inadequate, unrepresentative, and at risk. PLoS Biol 12:e1001888CrossRefGoogle Scholar
  48. Smith RC, Ainley D, Baker K, Domack E, Emslie S, Fraser B, Kennett J, Leventer A, Mosley-Thompson E, Stammerjohn S (1999) Marine ecosystem sensitivity to climate change: historical observations and paleoecological records reveal ecological transitions in the Antarctic Peninsula region. BioSci 49:393–404CrossRefGoogle Scholar
  49. Stammerjohn S, Massom R, Rind D, Martinson D (2012) Regions of rapid sea ice change: an inter-hemispheric seasonal comparison. Geophys Res Lett 39:L06501CrossRefGoogle Scholar
  50. Turner J, Lu H, White I, King JC, Phillips T, Hosking JS, Bracegirdle TJ, Marshall GJ, Mulvaney R, Deb P (2016) Absence of 21st century warming on Antarctic Peninsula consistent with natural variability. Nature 535:411–415CrossRefGoogle Scholar
  51. Votier SC, Bearhop S, Ratcliffe N, Phillips RA, Furness RW (2004) Predation by great skuas at a large Shetland seabird colony. J Appl Ecol 41:1117–1128CrossRefGoogle Scholar
  52. Wilson DJ, Lyver POB, Greene TC, Whitehead AL, Dugger KM, Karl BJ, Barringer JR, McGarry R, Pollard AM, Ainley DG (2017) South Polar Skua breeding populations in the Ross Sea assessed from demonstrated relationship with Adélie Penguin numbers. Polar Biol 40:577–592CrossRefGoogle Scholar
  53. Young EC (1990) Diet of the south polar skua Catharacta maccormicki determined from regurgitated pellets: limitations of a technique. Polar Rec 26:124–125CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Richard A. Phillips
    • 1
    Email author
  • Janet R. D. Silk
    • 1
  • Alison Massey
    • 1
  • Kevin A. Hughes
    • 1
  1. 1.British Antarctic SurveyNatural Environment Research CouncilCambridgeUK

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