Flexible foraging behaviour of a sexually dimorphic seabird: large males do not always dive deep ...

• Main Authors: Quillfeldt, Petra, Schroff, Simone, Noordwijk, Hendrika J. van, Michalik, Andreas, Ludynia, Katrin, Masello, Juan F., Justus Liebig University Giessen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Universitätsbibliothek Gießen 2011
• Subjects: Diving behaviour; Behavioural plasticity; Optimal foraging; Stable isotope analysis; Stable isotope mixing model; Sexual size dimorphism; Phalacrocorax atriceps; ddc570
• Online Access: https://dx.doi.org/10.22029/jlupub-155; https://jlupub.ub.uni-giessen.de//handle/jlupub/209

Sex differences in foraging behaviour have been explained by size dimorphism and/or avoidance of inter-sexual competition for depletable resources. To distinguish between these 2 hypotheses, we examined how intrinsic factors (sex-related differences) and extrinsic factors (year differences) shape the foraging behaviour of size-dimorphic imperial shags Phalacrocorax atriceps albiventer breeding at New Island, Falkland Islands/Islas Malvinas. We deployed time-depth and compass loggers to male and female imperial shags over 3 consecutive chick-feeding seasons. Males and females partly overlapped in coastal foraging areas, which were used mainly for benthic diving. Males additionally used offshore areas over deep water for shallow pelagic diving, suggesting that spatial segregation is involved in the avoidance of inter-sexual competition for food. Stable isotope data suggested differences in prey composition between the sexes, with consistently higher trophic levels in males, as expected for their larger size. ...