Recent trends in numbers of Crozet shags breeding at the Prince Edward Islands

Abstract

Numbers of Crozet shags Phalacrocorax [atriceps] melanogenis breeding at Marion Island decreased by more than 70% from 840 pairs in 1994/1995 to 220 pairs in 2003/2004 and then increased to some 500 pairs in 2008/2009. The trends are thought to have been influenced by breeding success, which averaged 0.30 and 0.66 chicks per pair per year during 1998/1999-2002/2003 and 2003/2004-2008/2009 respectively. There were similar trends in numbers breeding and breeding success of gentoo penguins Pygoscelis papua, which at Marion Island have a similar diet to Crozet shags, suggesting that both species may have been influenced by food availability. Numbers of Crozet shags breeding at Prince Edward Island approximately doubled between the summers of 2001/2002 and 2008/2009. In 2008/2009, some 600 pairs of Crozet shags were breeding at the Prince Edward Islands.