New research shows that female gannets travel farther than male gannets to find fish for their chicks in some years but not others.
Scientists have tracked breeding gannets from Grassholm Island in Wales over 11 years using tiny GPS devices and measuring isotopic signatures in their blood.
Male gannets flew an average of 220 km to forage for their young, while the females averaged 260 km. Some birds have traveled 1,000 kilometers in one trip.
The scientists also found that the two sexes chose different habitats and were foraging at different times of the day, but in some years they were more synchronized.
Dr Bethany Clark worked on the research while pursuing her Ph.D. at the University of Exeter’s Institute for Environment and Sustainability, and now works at BirdLife International.
“Our study used GPS tracking to investigate the behavior and the stable isotopes revealed information about their diet,” she said.
“The differences in foraging research we found might indicate that males and females respond differently to changes in environmental conditions, such as wind extent.
Their food preferences have been more consistent over the years: males tend to eat larger fish closer to the shore than females.
“Our results highlight the importance of long-term studies.”
“These birds are a true ocean wanderer – thousands of thousands travel at sea throughout their lives to find food. It should be a huge challenge for four and a half months to breed,” said Stephen Futter, professor of seabird ecology at the Lille Center, Heriot-Watt University, in Edinburgh. She chicks every year.
“The sexes are nearly identical, so the differences are not due to size. Rather, we believe that evils stay close to home because they establish and maintain the nest and possibly due to slight differences in taste.”
The study was funded by the Natural Environment Research Council and the European Union, and the field work was done thanks to the Royal Society for the Protection of Birds (RSPB).
The paper published in the journal Marine Ecology Advance Series, Titled: “Sexual Separation in Gannet Forage Over 11 Years: Movements vary but isotopic differences remain stable.”