Polar Biology

, Volume 31, Issue 3, pp 333–349

Introduced mammals coexist with seabirds at New Island, Falkland Islands: abundance, habitat preferences, and stable isotope analysis of diet

  • Petra Quillfeldt
  • Ingrid Schenk
  • Rona A. R. McGill
  • Ian J. Strange
  • Juan F. Masello
  • Anja Gladbach
  • Verena Roesch
  • Robert W. Furness
Original Paper

DOI: 10.1007/s00300-007-0363-2

Cite this article as:
Quillfeldt, P., Schenk, I., McGill, R.A.R. et al. Polar Biol (2008) 31: 333. doi:10.1007/s00300-007-0363-2

Abstract

The largest known colony of Thin-billed prions Pachyptila belcheri has been coexisting with introduced mammals for more than 100 years. Three of the introduced mammals are potential predators of adults, eggs and chicks, namely ship rats Rattus rattus, house mice Mus musculus and feral cats Felis catus. We here determine habitat preferences over three seasons and dietary patterns of the unique set of introduced predators at New Island, Falkland Islands, with emphasis on the ship rats. Our study highlights spatial and temporal differences in the levels of interaction between predators and native seabirds. Rats and mice had a preference for areas providing cover in the form of the native tussac grass Parodiochloa flabellata or introduced gorse Ulex europaeus. Their diet differed markedly between areas, over the season and between age groups in rats. During the incubation period of the prions in November–December, ship rats had mixed diets, composed mainly of plants and mammals, while only 3% of rats had ingested birds. The proportion of ingested birds, including scavenged, increased in the prion chick-rearing period, when 60% of the rats consumed prions. We used δ13C and δ15N to compare the importance of marine-derived food between mammal species and individuals, and found that rats in all but one area took diet of partly marine origin, prions being the most frequently encountered marine food. Most house mice at New Island mainly had terrestrial diet. The stable isotope analysis of tissues with different turnover times indicated that individual rats and mice were consistent in their diet over weeks, but opportunistic in the short term. Some individuals (12% of rats and 7% of mice) were highly specialized in marine-derived food. According to the isotope ratios in a small sample of cat faeces, rodents and rabbits were the chief prey of cats at New Island. Although some individuals of all three predators supplement their terrestrial diet with marine-derived food, the current impact of predation by mammals on the large population of Thin-billed prions at New Island appears small due to a number of factors, including the small size of rodent populations and restriction mainly to small areas providing cover.

Keywords

Ship rat House mouse Invasive species Stable isotopes 

Supplementary material

300_2007_363_MOESM1_ESM.pdf (1.1 mb)
Electronic appendix 1 (PDF 1146 kb)
300_2007_363_MOESM2_ESM.pdf (685 kb)
Electronic appendix 2 (PDF 685 kb)

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Petra Quillfeldt
    • 1
  • Ingrid Schenk
    • 2
  • Rona A. R. McGill
    • 3
  • Ian J. Strange
    • 2
  • Juan F. Masello
    • 1
  • Anja Gladbach
    • 1
  • Verena Roesch
    • 1
  • Robert W. Furness
    • 4
  1. 1.Max-Planck Institut für OrnithologieVogelwarte RadolfzellRadolfzellGermany
  2. 2.New Island Conservation TrustStanleyFalkland Islands
  3. 3.Scottish Universities Environmental Research CentreGlasgowUK
  4. 4.Institute of Biomedical and Life Sciences, Graham Kerr BuildingUniversity of GlasgowGlasgowUK

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