Ponds support higher bird diversity than rice paddies in a hilly agricultural area in Japan
The aim of the present study was to evaluate bird diversity (richness, abundance, and community composition) in three types of artificial wetlands (rice paddies, carp aquaculture ponds, and farm ponds for irrigation) while considering bird habitat groups and seasons and to reveal the environmental characteristics of wetlands (e.g. wetland type, water depth, and vegetation cover) associated with bird richness and abundance. Bird and environmental characteristics were surveyed in 30 sites (10 sites per wetland type) in the hilly agricultural area of central Japan, considering four bird groups (open-land, wetland, bush, and woodland) and three seasons (breeding, migrating, and wintering). Bird richness of each group was the highest in farm ponds, followed by carp ponds and then rice paddies, throughout the year, except for bush and woodland species. Abundance levels of open-land, woodland, and total species were significantly higher in farm ponds than in rice paddies and carp ponds in the wintering season (and also in migrating season for open-land species). Effects of wetland type, wetland area, vegetation cover on water surface, and slope of bank to bird species and abundance differed among bird groups. There were no differences in community compositions among wetland types, although significant differences were apparent among seasons. Therefore, for bird diversity conservation in hilly agricultural areas, (1) various wetland types creating a spatial–temporal heterogeneity of environments is important, (2) preserving ponds rather than rice paddies would be effective, and (3) steeper slopes and richer vegetation cover on water surfaces should be considered for waterbirds.