1. Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, People's Republic of China
2. Department of Ornithology, Max Planck Institute for Biological Intelligence, Seewiesen 82319, Germany
3. Edward Grey Institute, Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
4. Academy of Forestry Inventory and Planning, National Forestry and Grassland Administration, Beijing 100714, People's Republic of China
5. School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, People's Republic of China