Yokoyama reservoirs were constructed in 1866 to keep water for paddy fields, and are located near Mukumoto town, about 20 km from the sea. The best season is winter. Many ducks winter in this reservoir; Mallard, Spot-billed Duck, Tufted Duck, Common Pochard, Gadwall, and Smew. The other water birds are Great Cormorant, Great Crested Grebe (rare), Little Grebe and Coot. Long-tailed Rose Finch, Rustic Bunting, Brawn-eared Bulbul and various tits are found in surrounding woods. Goshawk, Sparrow Hawk and Buzzard are sometimes seen.