Middle-sized Procellariidae replace each feather in order once a year. We measured total mercury contents ([Hg]) of each feather of 3 individuals of Streaked Shearwaters Calonectris leucomelas found dead in March in Kyoto, Japan. [Hg] was moderate in the back feathers, highest in the inner primaries (P1, P2), decreased to be low in the outermost primary (P10) and all tail feathers (R1 – R6). The excretion of mercury through molting partly explains the seasonal change of the mercury contents in the body.
