Sexually Distinct Daily Activity Patterns of Blue-Eyed Shags in Antarctica

Abstract

Sexually distinct rhythms of nest attendance were documented for blue-eyed shags (P. atriceps) in Antarctica. Males attended the nest from .apprx. 00:00-12:00 and foraged from .apprx. 12:00-24:00 h. Female activity patterns were the opposite. Timing of male courtship occurred around 12:00 during the prelaying and laying-incubation periods, and timing of chick feeding was also sexually distinct. Males fed chicks in the early morning and late evening; females fed chicks in the afternoon. The rhythms were colony-wide and partially influenced by times of sunrise and sunset. Although specific adaptive pressures influencing these patterns are unknown, intersexual foraging competition is presented as a possible explanation relative to other theories.