2019 Volume 68 Issue 2 Pages 307-315
The Eurasian Woodcock Scolopax rusticola is a nocturnal game bird that rarely vocalizes outside the breeding season. It overwinters in a broad area of Japan, from Honshu to the Ryukyu Islands. Lack of population information is an issue when considering the conservation management of this species in Japan, making it important to develop effective monitoring methods. The Ministry of the Environment has drawn up a manual for spotlight survey to confirm its presence; however, distribution and population estimation methods using presence-only data obtained from such censuses have not been developed. To estimate the distribution and population size of the woodcock, we conducted a spotlight survey and constructed a maximum entropy model on Sado Island, Japan. Cultivated rice fields form the main foraging habitat of woodcocks on Sado Island. Woodcocks were more likely to be found in areas with large fields and high average temperatures. The model estimated the existence of 36.8 (25.12–43.12) km2 habitat on Sado Island, and predicts 79 (54–92) wintering individuals. From conservation efforts for the Crested Ibis Nipponia nippon on Sado Island, it is known that the amount of biomass, including earthworms, has increased as a consequence of environment-friendly farming. The quality of rice fields available as foraging sites for woodcocks could be improved by further environment-friendly farming. The combination of spotlight survey and maximum entropy model shown in this study is effective for monitoring the distribution and population trends of this species. It will be necessary to monitor the distribution of woodcocks across the country in order to conduct conservation management of the species by implementing wildlife protection areas and temporary game preserves.
