Polar Biology

, Volume 40, Issue 3, pp 577–592 | Cite as

South Polar Skua breeding populations in the Ross Sea assessed from demonstrated relationship with Adélie Penguin numbers

  • Deborah J. Wilson
  • Philip O’B. Lyver
  • Terry C. Greene
  • Amy L. Whitehead
  • Katie M. Dugger
  • Brian J. Karl
  • James R. F. Barringer
  • Roger McGarry
  • Annie M. Pollard
  • David G. Ainley
Original Paper


In the Ross Sea region, most South Polar Skuas (Stercorarius maccormicki) nest near Adélie Penguin (Pygoscelis adeliae) colonies, preying and scavenging on fish, penguins, and other carrion. To derive a relationship to predict skua numbers from better-quantified penguin numbers, we used distance sampling to estimate breeding skua numbers within 1000 m of 5 penguin nesting locations (Cape Crozier, Cape Royds, and 3 Cape Bird locations) on Ross Island in 3 consecutive years. Estimated numbers of skua breeding pairs were highest at Cape Crozier (270,000 penguin pairs; 1099 and 1347 skua pairs in 2 respective years) and lowest at Cape Royds (3000 penguin pairs; 45 skua pairs). The log–log linear relationship (R2 = 0.98) between pairs of skuas and penguins was highly significant, and most historical estimates of skua and penguin numbers in the Ross Sea were within 95 % prediction intervals of the regression. Applying our regression model to current Adélie Penguin colony sizes at 23 western Ross Sea locations predicted that 4635 pairs of skuas now breed within 1000 m of penguin colonies in the Ross Island metapopulation (including Beaufort Island) and northern Victoria Land. We estimate, using published skua estimates for elsewhere in Antarctica, that the Ross Sea South Polar Skua population comprises ~50 % of the world total, although this may be an overestimate because of incomplete data elsewhere. To improve predictions and enable measurement of future skua population change, we recommend additional South Polar Skua surveys using consistent distance-sampling methods at penguin colonies of a range of sizes.


Distance sampling Environmental change Pygoscelis adeliae Seabirds South Polar Skua Stercorarius maccormicki 



We thank G. Barclay, J. Whitehead, Q. Barr-Glintborg and R. Hunter for assistance in the field, K. Drew for data compilation, Antarctica New Zealand and the U.S. Antarctic Program for logistical support, and the New Zealand Ministry for Primary Industries’ Antarctic Fisheries Working Group for discussions. We are grateful to W. Fraser and E. Woehler for insights into skuas and penguins in the Antarctic Peninsula and East Antarctic regions, respectively; W. Fraser of the Palmer LTER also provided unpublished data on skua numbers in the middle portion of the Antarctic Peninsula. Similarly, we thank C. Harris for access to the Important Bird Areas data base to check on our gleaning of the literature for skua numbers in the Antarctic Peninsula. We thank reviewers and editors for their valuable comments on previous versions of this paper. This research was conducted in compliance with New Zealand Ministry of Foreign Affairs and Trade Preliminary Environmental Evaluation Notification/Permits (K121-1112; K121-1213 and K122-1415-A). It was supported by contestable Grants (C01X1226 and C01X1001) and core funding for Crown Research Institutes from the New Zealand Ministry of Business, Innovation and Employment’s Science and Innovation Group, by the New Zealand Ministry for Primary Industries (MPI17238-S01-LC), by the New Zealand Department of Conservation (Science and Capability), and by Grant ANT-0944411 from the U.S. National Science Foundation. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US government.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Human and animal rights

All applicable international, national, and institutional guidelines for the care and use of animals were followed.

Supplementary material

300_2016_1980_MOESM1_ESM.docx (90 kb)
Supplementary material 1 (DOCX 90 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Deborah J. Wilson
    • 1
  • Philip O’B. Lyver
    • 2
  • Terry C. Greene
    • 3
  • Amy L. Whitehead
    • 4
  • Katie M. Dugger
    • 5
  • Brian J. Karl
    • 2
  • James R. F. Barringer
    • 2
  • Roger McGarry
    • 6
  • Annie M. Pollard
    • 7
  • David G. Ainley
    • 8
  1. 1.Landcare ResearchDunedinNew Zealand
  2. 2.Landcare ResearchLincolnNew Zealand
  3. 3.Department of ConservationChristchurchNew Zealand
  4. 4.National Institute of Water and Atmospheric ResearchChristchurchNew Zealand
  5. 5.U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and WildlifeOregon State UniversityCorvallisUSA
  6. 6.Owairaka, AucklandNew Zealand
  7. 7.Coos BayUSA
  8. 8.H. T. Harvey and Associates Ecological ConsultantsLos GatosUSA

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