Abstract:
Knowledge of seabird distribution is critical toward understanding their foraging ecology. For the first time, this study investigated the foraging behaviour of gentoo penguins at sub-Antarctic Marion Island using global positioning system (GPS) loggers and temperature depth recorders (TDRs). During August 2014, loggers were deployed on penguins brooding recently hatched chicks. The loggers were only retrieved five days after deployment to facilitate capturing multiple tracks of each individual. This resulted in 32 GPS tracks with corresponding TOR tracks from nine penguins. Firstly, this study revealed that the shallow inter-island shelf between Marion and Prince Edward Island is an important foraging area. This area is likely to provide predictable prey to the gentoo penguin as it provides an ideal habitat for three main dietary components of these penguins: Nototheniid fish, and a benthic (Nauticaris marionis) and pelagic (Euphuausia vallentini) crustacean species. Additionally, for the first time, visualization of tracks revealed two classes of trips. Short trips, which we predict to be for self-maintenance as these trips were followed by a rest period on the beach overnight; as determined from GPS loggers. Tracks of greater distance and duration were always followed by adult birds returning to the colony, where we predict feeding of chicks to have occurred. To our knowledge this is the first study to associate short trips with self-maintenance. We suggest that due to the close proximity of a predictable foraging area for these penguins at Marion Island, there is minimal energetic cost to return to land after self-pro visioning. Hence, unlike other seabirds, Gentoo penguins at Marion Island are uniquely afforded the opportunity for short self maintenance trips.
