Adaptability of great cormorants Phalacrocorax carbo in a coastal environment demonstrated by their exploitation of introduced prey species and use of artificial breeding sites

Abstract

An analysis of the contents of regurgitations of great cormorant Phalacrocorax carbo chicks at two coastal colonies in South Africa, one on an offhore island (St Croix) and the other at a saltworks in an estuary (Swartkops), revealed that the diet was dominated by introduced freshwater and estuarine fish. Most other prey species were indigenous euryhaline fish, and from the size ranges of the estuary-dependent species it was clear that they had been obtained in estuaries. Great cormorants in this coastal environment have learned to exploit introduced fish species, but use offshore islands as safe breeding sites, unless suitably safe artificial sites are created near their preferred foraging areas.

Keywords: chick regurgitations, diet, St Croix Island, Swartkops River

African Journal of Marine Science 2002, 24: 317–321