Population declines and heavy metal exposure of Swinhoe’s Storm Petrels (Oceanodroma monorhis) breeding on the southwest coast of Korea

We investigated the population dynamics of globally near-threatened Swinhoe’s Storm Petrels on Kugul and Chilbal islets where >90% of the world breeding population have resided for >25 years. We also determined the levels of six heavy metals in the seabird species as a possible factor affecting reproduction. Of the 892 and 307 marked burrows since 1986, the breeding density of Swinhoe’s Storm Petrels has changed significantly, based on a 55% decline at Kugul islet, and a 39% decline at Chilbal islet, suggesting that this species has suffered an extensive population decline. Of the individuals studied, five Swinhoe’s Storm Petrels and two Streaked Shearwaters had >8.0 μg/g Pb in tissues, which is a potentially lethal level in avian species. Given that substantial changes in their breeding populations may occur in a limited breeding colony, ecological threats including environmental pollutants warrant attention for global conservation of these birds.