Hatching control of Black-tailed Gulls for the conservation of Japanese Red Pine Forest in Matsushima Bay, Miyagi Prefecture

Abstract

Abstract. Japanese Red Pine Pinus densiflora forests are declining on several islands in Matsushima Bay, northeastern Japan where Black-tailed Gulls Larus crassirostris breed. Recently, the gull population has increased. In order to conserve the forests, gull eggs were immersed in cooking oil (Oiling) to prevent them from hatching, and the effect on the inorganic soil nitrogen content of the Isozaki fishery port site in Matsushima Bay was evaluated. There were no significant differences in the density of nests, number of eggs, number of nests without eggs, and percentages of nests without eggs between oiling and control sites. No eggs hatched at the oiling site, whereas 38-45% hatched at the control site. Hatching of Black-tailed Gull eggs was completely prevented by oiling. Nevertheless, inorganic nitrogen content in surface soils did not differ between two sites. Low percentages of hatching at the control site would result in a reduced nitrogen supply to the soil.