The streaked shearwater (Calonectris leucomelas) breeds along the western Pacific coast, and winters in Australia and Southeast Asia. Several nesting sites are found on islands off the Japanese coast, and previous reports have noted that the males and females exhibit different mating calls. This research, implemented at a breeding colony on Kanmuri Island, Kyoto Prefecture, investigated the relationship between sex and frequency of call in Calonectris leucomelas. Two distinct calls, one high and one low, were identified (Fig. 1). Observations of mounting birds showed that all (96) of mounting birds vocalized the high call, while 87.7% of the mounted birds produced the low call. These results clearly indicate that the high call to the male.