1. Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, Japan
2. Department of Zoology and Laboratory of Ornithology, Faculty of Science, Palacký University, Olomouc, Czech Republic
3. Cornell Laboratory of Ornithology, Cornell University, Ithaca, NY, USA
4. Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Hokkaido, Japan
5. Department of Ecology, Faculty of Science, Charles University, Prague, Czech Republic