Pleistocene seabirds from Shiriya, northeast Japan: systematics and oceanographic context

ABSTRACT

Seabirds are higher-order predators in the marine ecosystem and hence good indicators of the marine environment. Although the North Pacific has been the focal area for investigations of seabird faunal dynamics, the Pleistocene seabird fossil record has been scarce in the western North Pacific. Here, remains of 32 species of seabirds and related taxa (Anatidae, Podicipedidae, Gaviidae, Diomedeidae, Hydrobatidae, Procellariidae, Phalacrocoracidae, Scolopacidae, Laridae, and Alcidae) are reported from the middle–late Pleistocene Shiriya local fauna, northeastern Japan (Marine Isotope Stages 9 and 5e, ~ 320 and ~ 120 ka). This is the first substantial Pleistocene seabird fauna reported from the region so far, and includes globally first fossil records for Cepphus carbo and extant species of Aethia. The fauna also includes three extinct species, Shiriyanetta hasegawai, Mancalla? sp., and Uria onoi, the former two of which were flightless. The occurrence of immature individuals indicates that at least two species had nearby breeding sites. The seabird populations had probably been sustained by enhanced oceanic productivity in this area during their age, but oceanographic fluctuations in the subsequent glacial period, including the probable disappearance of a nearby oceanic front, would have seriously affected their subsistence, likely causing local extinctions of some species.

KEYWORDS:

• Climate change
• extinction
• fossil birds
• oceanic front
• Pleistocene
• seabirds

Acknowledgments

Sincere thanks are given to the late Zenji Nakajima, who kindly provided YH with specimens he collected. Fieldwork was kindly assisted by staffs at the Shiriya Quarry Complex of Nittetsu Mining. The following individuals generously accommodated works at their collections during the research: Yoshiya Odaya (AMB), Maureen Flannery (CAS), Masaki Eda (EP), Fumihito Takaya (HUNHM), Akihiro Koizumi and Takeshi Muramatsu (ICM), K. Garrett (LACM O), Samuel A. McLeod and Vanessa R. Rhue (LACM VP), Carla Cicero and Jessie A. Atterholt (MVZ), Makoto Manabe, Chisako Sakata, and Yuri Kimura (NSMT PV), Isao Nishiumi (NSMT AS), Kesler A. Randall (SDSNH), Patricia A. Holroyd (University of California Museum of Paleontology, Berkeley, California, USA), Brian K. Schmidt, Christopher M. Milensky, Mark Florence, and Helen F. James (USNM), Robert C. Faucett (UWBM), and Takeshi Yamasaki and Tomoko Imamura (YIO). The authors express thanks to N. Adam Smith, Naoki Kohno, Yutaka Watanuki, Nobuhiko Sato, and Masaki Eda for providing useful information and discussion, and to the two anonymous reviewers for their comments. Visits to American institutions were partly supported by a Kyoto University Foundation grant to JW.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary materials

Supplemental data can be accessed here.

Additional information

Funding

This work was partly supported by the Kyoto University Foundation;