New insights into the foraging behaviour and habitat of Rockhopper Penguins breeding at Staten Island

RAYA REY ANDREA; ROSCIANO, NATALIA G; LÜTHI, BENO; PÜTZ, KLEMENS

Bristol

Congreso; 8th International Penguin Conference; 2013

Bristol University

AbstractUnderstanding the foraging behaviour and foraging habitat of species is crucial to various applications in ecology and conservation. The aim of this study was to analyze the foraging habitat characteristics of female rockhopper penguins during brooding at Staten Island using GPS and time-depth data, and to ascertain if different foraging strategies persist in the population. Using MaxEnt modelling, we applied ecological niche models to establish the oceanographic variables influencing the utilized brooding habitat. The most important oceanographic parameters predicting the at-sea distribution of the birds studied were the proximity of the shelf break and the sub Antarctic front (= SAF). A cluster observation analysis revealed two different foraging strategies: The first one was determined by bathymetry, sea surface temperature and the SAF (= coastal strategy), whereas the most important variables for the second group were the SAF, the shelf break and chlorophyll values (= pelagic strategy). Dive characteristics differed slightly between the two groups. Bottom time, number of wiggles, mean and maximum dive depth were higher in pelagic compared with coastal penguins. Stable isotope analysis of whole blood samples showed contrasting values for δ13C (-21.6 ± 0.5, -22.5 ± 0.4, for coastal and pelagic birds respectively) but no differences for δ15N (9.9 ± 0.4, 9.3 ± 0.4, respectively). The carbon value for coastal birds was higher than expected. As whole blood sampling integrated both, brooding and the incubation trip of the females, a potential explanation might be that coastal birds used more than one foraging strategy at a time (pelagic and coastal), or used a pelagic strategy during incubation and a coastal strategy while brooding. Given the known distribution of females during incubation from previous studies, the second explanation appears more plausible. The combination of these two strategies in the population during brooding could be advantageous as birds were reducing spatial overlapping while feeding within the same trophic level. Finally, this study highlights the importance of the SAF for rockhopper penguins, an oceanographic feature susceptible to changes in location following global warming and subsequent implications for conservation measures.