Geographic variation in the acoustic signals of black-billed magpies (Pica pica) in South Korea and Japan

Black-billed magpies (Pica pica) are a highly sedentary species due to their short and round wings, which are not adequatefor long distance flights. We investigated geographic variation in the vocal signals of magpies residing in SouthKorea and Japan (subspecies sericea). Based on the magpie’s limited dispersal ability, we predicted that the variation invocal signals of black-billed magpies could be explained by geographic barriers such as mountain ranges and straits.We analyzed four-syllable chatter calls of magpies from five localities in South Korea, which are separated by mountainranges (Seoul, Daejeon, Daegu, Gwangju, and Busan), and two island localities separated from the mainland by straits(Jeju in Korea and Saga in Japan). We found significant differences in the characteristics of magpie chatter calls recordedin the seven localities, and the variation pattern was independent among the variables. Mainland-island differentiationand north-south differentiation were observed. In general, magpies on Saga were the most distinctive. North-south differentiationwas observed among the Korean mainland localities. However, the pattern was not related to the presence ofputative geographic barriers. We hypothesize that the patterns of geographic variation in the structure of magpie chattercalls residing in South Korea might have been shaped by a sudden expansion of magpies followed by low level of localisolation, which may have led to vocal differentiation. Along with elucidating the vocal environment of Korean magpiepopulations, more extensive sampling is needed to clarify the functional aspects of geographic variation in the vocalsignals of Korean magpies.