Effect of Limited-scale Improvement Works on the Maintenance of Food for Japanese Crested Ibis in Hilly and Mountainous Areas

This study examines whether the adequate population of loaches, one of the main food resources of Japanese Crested Ibis (Toki), can be maintained by the implementation of limited-scale improvement works of the habitat. As a result of the monitoring survey with the mark-recapture method, it was confirmed that the number of loaches was estimated to be 1.5 per m² in the study paddy field, and 5.2 per m² in the study canal, which in turn, exceeded the necessary amount for feeding Japanese Crested Ibis reported by Japan Wildlife Research Center. The major factors leading to this favorable outcome are considered to be the existence of the intercepting drain in the paddy field, the canal fishway, the paddy field fishway, and environment-conscious canal. It is also supposed that the loaches' range of activity is quite limited in comparison with the spatial extent of improvement works. These outcomes leads to a conclusion that the limited-scale improvement works are effective for the maintenance of loach population.