As a part of ‘theme 6’ ecosystem and biodiversity research program, ArCS researchers studied seabirds breeding on St Lawrence Island, Northern Bering Sea. This season is the third year of our fieldwork, which started in 2016. Researchers from NIPR, Hokkaido University, and University of Alaska Fairbanks worked together with native guides from St. Lawrence Island, from mid-July to the end of August. I traveled to join the fieldwork from 31 July – 18 August 2018.
After arriving at Savoonga, an Eskimo village on the island, we started visiting nearby seabird colonies. We soon felt something wrong about breeding seabirds this year – the number of breeding birds was so low than previous years. We visited our research site where we attached geolocators on thick-billed and common murres last summer, but the cliff ledges were empty with no sign of breeding murres. As we walked along the shore, we found many carcasses of adult murres washed ashore. Such ‘die-off’ of murres was reported widely in the coastal regions of Northern Bering Sea in this summer. ‘Die-off’ of adult murres is a rare phenomenon, and it is widely reported in media across Alaska. According to our monitoring study, not only murres but also least and crested auklets had a poor breeding season as well. We found many auklet chicks died in the nest, likely due to starvation.
Why seabirds in Northern Bering Sea died in large numbers and bred poorly in this summer? We do not know the answer yet, but the possible causes might be food shortage and wildlife disease. The authority in Alaska has inspected seabird carcasses but detected no signs of infectious diseases so far. Sea ice extent showed a historic low in this spring in the entire Northern Bering Sea, including the coastal regions around Savoonga. Did sea ice loss cause the shift of local marine ecosystem and affect the food of seabirds? We plan to investigate this further, by analyzing the seabird diet and physiological samples collected this year and by comparing the results between this year and previous years.
Akinori Takahashi (NIPR / a member of Theme 6)