Trends in numbers of crowned cormorants in South Africa, with information on diet

  • RJM Crawford
  • BM Dyer
  • D Geldenhuys
  • AB Makhado
  • RM Randall
  • L Upfold
  • J Visagie
  • L Waller

Abstract

During 2008–2012, the number of crowned cormorants Phalacrocorax coronatus breeding in South Africa was c. 1 900 pairs, compared to 1 700 pairs for 1977–1981. Numbers at 10 islands in the Western Cape province fluctuated around a level of 1 100 pairs from 1991/1992 to 2011/2012, 300 more than from 1978/1979 to 1990/1991. These increases are attributable to the discovery of more colonies and an increased frequency of counting at the 10 islands after 1990/1991. The overall number of crowned cormorants breeding in South Africa is thought stable in the long term. Crowned cormorants feed mainly on small, inshore fish species that are not harvested by humans. Clinidae dominated the diet at 10 colonies adjoining the open sea, whereas Gobiidae contributed most food of birds at three colonies in a lagoon. The stability of the crowned cormorant population contrasts with decreases of some other seabirds endemic to southern Africa that feed primarily on prey that is exploited by fisheries. The crowned cormorant population decreased in the Northern Cape and small numbers initiated breeding at colonies to the east of Cape Agulhas at the turn of the century, but most of the population continues to breed to the west of Cape Agulhas. In some instances the availability of suitable breeding habitat may limit numbers breeding.

Keywords: breeding habitat, Clinidae, Gobiidae, Phalacrocorax coronatus, population trend

African Journal of Marine Science 2012, 34(3): 411–424

Author Biographies

RJM Crawford
Oceans and Coasts, Department of Environmental Affairs, PO Box 52126, Cape Town 8001, South Africa; Animal Demography Unit, University of Cape Town, Rondebosch 7701, South Africa
BM Dyer
Oceans and Coasts, Department of Environmental Affairs, PO Box 52126, Cape Town 8001, South Africa
D Geldenhuys
Cape Nature, Private Bag X29, Rondebosch 7701, South Africa
AB Makhado
Oceans and Coasts, Department of Environmental Affairs, PO Box 52126, Cape Town 8001, South Africa
RM Randall
South African National Parks, PO Box 176, Sedgefield 6573,South Africa
L Upfold
Oceans and Coasts, Department of Environmental Affairs, PO Box 52126, Cape Town 8001, South Africa
J Visagie
Cape Nature, Private Bag X29, Rondebosch 7701, South Africa
L Waller
Animal Demography Unit, University of Cape Town, Rondebosch 7701, South Afric; Cape Nature, Private Bag X29, Rondebosch 7701, South Africa
Section
Articles

Journal Identifiers


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