| In this study, we investigated the colonization status of the Little Tern Sterna albifrons sinensis (hereinafter LT) in Class A rivers in the Kanto region and the environmental factors that contribute to its presence along the Kinugawa River. Between 1991 and 2013, colonies of LT were observed at 20 sites on 7 rivers in 5 water systems. The LT established colonies at 3 sites in estuaries, 14 sites in inland gravel beds,and 3 sites in developed lands. The size of each colony ranged from 0.2 to 15 hectares. However, most colonies were formed on gravel beds of less than 5 hectares. In the proximity of the Kinugawa River, gravel beds, open water, and wet grasslands were selected as important environments for the presence of the LT.We suggest considering the LT nesting habitats on several hectares when excavating the river channel for flood control. Furthermore, restoring the foraging habitat of the LT, such as the ecotone of wetland weeds, shallows, or flood plain water bodies, could potentially lead to the creation of suitable habitats for the LT. |
