Regional differences in the song characteristics of Pallas’s Leaf Warbler Phylloscopus proregulus in north-east Asia

Intra-specific variation in avian songs can be complex and often remains understudied in species that exhibit pronounced dialectal
differentiation. Pallas’s Leaf Warbler Phylloscopus proregulus is a migratory bird that breeds across mountainous forests from southern
Siberia to the Far East of northern Asia. However, to date, studies on the songs of this species have been limited to the western area of their
breeding range. Here, we document song differences among Pallas’s Leaf Warbler populations across north-east Asia. The population in
the Mongolia–Baikal region exhibited significant differences in its acoustic properties from the populations of the Amur River basin and
South Korea. On the other hand, the songs of the Amur River basin and South Korea were not different from each other. Considering the
forest connectivity between the Amur River basin and Korean peninsula, our findings suggest population structure in Pallas’s Leaf Warblers
between the Mongolia–Baikal region and the Amur–Korea region. To better understand the relationships between these two populations,
a combination of bioacoustic and population-genetic studies coupled with migratory monitoring is recommended.