POPULATION AND BREEDING OF THE GENTOO PENGUIN PYGOSCELIS PAPUA AT MARION ISLAND, 1994/95–2002/03

  • R JM CRAWFORD Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • J. COOPER Avian Demography Unit, University of Cape Town, Rondebosch 7701, South Africa
  • M DU TOIT Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • M D GREYLING School of Biological Sciences, University of Pretoria, Pretoria 0002, South Africa
  • B HANISE Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • C L HOLNESS Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • D G KEITH Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • J L NEL Council for Scientific and Industrial Research, P.O. Box 320, Stellenbosch 7599, South Africa
  • S L PETERSEN Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • K SPENCER Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • D TSHINGANA Marine & Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa.
  • A C WOLFAARDT Western Cape Nature Conservation Board, Private Bag X9086, Cape Town 8000, South Africa
Keywords: breeding success, gentoo penguin, Marion Island, population trend, Pygoscelis papua, Subantarctic

Abstract

The numbers of gentoo penguins Pygoscelis papua breeding at subantarctic Marion Island fell by 40% from 1994/95 to 2002/03, from 1 352 pairs to 806 pairs. Apart from a slight increase in 1998/99, there was a steady decrease in numbers breeding between 1995/96 and 2000/01, when the population stabilized. There is indication that in some years not all breeders nested and that some birds relocated to another colony after disturbance. From first clutches, pairs on average fledged between 0.01 chicks in 1997/98 and 0.58 chicks in 2002/03 (mean 0.38 ± 0.21). In 1994/95, replacement clutches increased the overall production of fledged chicks by 11%. Based on demographic parameters measured at other localities, the production of chicks at Marion Island was inadequate to maintain the population during the period 1995/96–2000/01. Consistency in trends in breeding success at five colonies suggests that factors operating at a mesoscale, rather than those specific to particular colonies, often influenced breeding success. Laying was later than normal in 1997/98, when there was almost total breeding failure with large losses of eggs and small chicks to returning Subantarctic skuas Catharacta antarctica. Future research on this Near Threatened species at Marion Island must take full account of its susceptibility to human disturbance.

Afr. J. mar. Sci. 25: 463–474
Published
2005-05-12
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X