Expansion of the range of the Light-vented Bulbul Pycnonotus sinensis into mainland Japan

Abstract

The distribution of Light-vented Bulbul Pycnonotus sinensis has been expanding in East Asia in recent decades. Since the 2000s it has even bred sporadically in mainland Japan, in both Kyushu and Honshu, which it may have reached by natural dispersal. In this study, we aimed to clarify the origins of the birds seemingly colonising western Japan. First, we reviewed observations of the species in South Korea and western Japan and clarified spatiotemporal changes in its distribution since the 2000s. Second, we captured Light-vented Bulbul in Kitakyushu, where it has been observed since 2017 and compared its morphological characteristics and ND2 sequence in the mitochondrial DNA with those of other populations. We obtained three key results: 1) the number of observations of the Light-vented Bulbul has increased since the late 2000s in western Japan, which is consistent with the timing of its expansion in South Korea; 2) individuals captured in Kitakyushu had morphological characteristics similar to those of P. s. sinensis in China; and 3) we observed multiple haplotypes in the Kitakyushu population, which were all included in the cluster of P. s. sinensis and P. s. hainanus, but not included in the cluster of P. s. formosae in Taiwan, P. s. orii in the Yaeyama Islands, or in the unidentified subspecies on Okinawajima Island. These results suggest that China is the origin of individuals recently observed in western Japan, and it is considered likely that dispersal has occurred naturally from the Eurasian continent via the Korean Peninsula. Since the Light-vented Bulbul has already become established, and is still increasing in numbers, in southeastern South Korea, observations are also likely to increase in western Japan.