Foraging behavior of Ad,lie penguins during incubation period in Lutzow-Holm Bay

The diving behavior of Ad,lie penguins Pygoscelis adeliae was investigated using time-depth recorders during the incubation period in the fast sea-ice area of Lutzow-Holm Bay, Antarctica. Dive profiles and activity/time allocation suggested that penguins were obligated to walk on the fast-ice for 90-100 km until a polynya, which they used as an access to the pack-ice zone. Dive depth did not differ between males and females, though males' dive duration was longer than that of females. Dive depth was slightly shallower and dive duration was shorter during the incubation than during the chick-rearing phase. Birds dove throughout the day, although less frequently around midnight, and there was no clear diel change in dive depth. This daily dive pattern during incubation period was similar to that previously observed during the chick-rearing period in a fast sea-ice area, but differed from that observed in sea-ice-free area. Variations in diving behavior resulted from different environmental conditions, such as foraging area with different sea-ice condition, as well as from different life history strategies.