”Latitude-Longitude Index” for wintering distribution locations of various bird species in Japan

   The species temperature index (STI), which is the mean temperature of the distribution area for bird species, has been calculated to evaluate the response of birds to climate change. In Japan, the STI for the breeding season has been calculated based on the results of the “Japan Breeding Bird Atlas.” Since the effects of climate change are more pronounced during the wintering season of birds (Lehikoinen et al. 2021), it is important to know the STI for the wintering season in Japan. We surveyed to determine the wintering distribution of birds in Japan between January 2016 and February 2022. However, the 40 km grid to collect distribution information used in this survey included areas of low to high elevation in the steep terrain of Japan which made the temperature differences within the grid too large to show STI. Since the Japanese archipelago extends from southwest to northeast, the distribution of any bird species in the Japanese archipelago can be indicated by the value obtained by adding latitude and longitude. Therefore, we calculated ”Latitude-Longitude Index” values that describe the distribution of various bird species during the wintering season in Japan to replace the STI. Here we present this method and propose it is a useful approach for studying the effects of climate change on birds.</p

Data from: Seasonality in spatial distribution: climate and land use have contrasting effects on the species richness of breeding and wintering birds

Aim: Many studies have examined large-scale distributions of various taxa and their drivers, emphasizing the importance of climate, topography, and land-use. Most studies have dealt with distributions over a single season or annually without considering seasonality. However, animal distributions and their drivers can differ among seasons because many animals migrate to suitable climates and areas with abundant prey resources. We aim to clarify seasonality in bird distributions and their drivers. Location: Japan. Methods: We examined the effects of climate (annual mean temperature, snow depth), topography (elevation), and land use (extent of surrounding habitat) on bird species richness, in the breeding and wintering seasons separately, using nationwide data (254 forest and 43 grassland sites, respectively). We separately analyzed the species richness of all species, residents, short-, and long-distance migrants in forests and grasslands. Results: In the breeding season, the annual mean temperature negatively affected all groups (except for forest and grassland residents), and the extent of surrounding habitat positively affected many groups. By contrast, in the wintering season, temperature positively affected all groups (except for forest residents), and the extent of surrounding habitat positively affected only grassland long-distance migrants. In both seasons, the species richness of forest and grassland residents was high in regions of moderate and high temperature, respectively. Moreover, snow depth negatively affected all forest groups in the wintering season. Mapping expected species richness suggested that regions with different climates served as habitats for different groups during different seasons. Main conclusions: All regions were important bird habitats depending on the season, reflecting the contrasting effects of temperature across seasons. In the breeding season, surrounding land-use was also an important driver. To understand the seasonal role that each region and environment plays in maintaining species/communities, a large-scale study considering both environmental seasonality and species distribution is needed