Recruitment and age at first breeding in the Antarctic Shag at Harmony Point, South Shetland Islands

Abstract

Recruitment rate and age at first breeding are key parameters in population dynamics. In colonies of the Antarctic Shag (Leucocarbo bransfieldensis) in the South Shetland Islands, Antarctica, a decline in the number of breeding pairs has been reported, attributed to reduced food availability near the colonies due to regional overfishing. In this context, understanding how these parameters are affected is essential for assessing the dynamics of this species. Recruitment rate and age at first breeding differences were estimated for both sexes using data from 2000 to 2005 from a chick ringing program carried out at Harmony Point (62°18’S, 59°11’W, Nelson Island, South Shetland Islands). Results showed a low recruitment rate(8.61%), particularly in males (3.57%), and an early age at first breeding (between 2 and 3 years old). These patterns might be related to the overall decline in breeding pairs, and under conditions of low food availability, post-fledging mortality or migration to other colonies could also occur.