Feather mercury concentration in streaked shearwaters wintering in separate areas of southeast Asia

We measured mercury concentration ([Hg]) and nitrogen stable isotope values (δ15N) in tail feathers that were replaced during the non-breeding period of streaked shearwaters Calonectris leucomelas that bred on 3 islands in Japan. The birds’ year-round movements were tracked and their breeding status was monitored. [Hg] was greater in males than in females, and was greatest in those birds spending their non-breeding period in the South China Sea (3.1 ± 1.5 µg g-1 dry weight), moderate in birds in the Arafura Sea (1.5 ± 0.7 µg g-1), and lowest in birds in the Pacific Ocean north of New Guinea (0.8 ± 0.4 µg g-1). Adverse effects of feather [Hg] on breeding status were not observed. This regional variation in feather [Hg] might partly reflect differences in the intake of Hg between these non-breeding areas in addition to accumulation during the late breeding period and the southward migration period