Winter bird communities in the heterogeneous farmlands of the Aso region in Japan

Abstract

Surveys of overwintering birds were conducted in a heterogeneous landscape, composed of paddy land, grassland, and mosaic agricultural land types, in the Aso region of Japan. Overall species richness and mean abundance were higher in paddy land types compared with the other two land types. Birds showed species-specific habitat preferences, with 26 species (56.5%) only being found on one of the three farmland types. Using canonical correspondence analysis, wider-ranging species were separated to species preferring forest and shrub vegetation sites compared with paddy field–dominated sites along the first axis. The environmental factors that explained individual abundance by generalized linear mixed models also differed among species and were dependent on the degree of paddy field, grass, shrub, and broad spatial forest cover. The most frequently detected bird species, Hypsipetes amaurotis, was positively correlated with the percentage of forests in paddy fields and grasslands at the local scale, where forests were rare. In conclusion, paddy lands that extend into valleys represent important habitat promoting high bird diversity during the wintering period, with the other two land types also supporting many species in this region at the landscape level. Keywords: Agricultural land use, Habitat range, Landscape Heterogeneity, Paddy field