Impact of illumination of long marine bridges on birds in surrounding Strait area

The construction plans of long marine bridges on the three Honshu-Shikoku Bridge Routes were approved in October, 1973. After more than a quarter of a century, the construction of all three Routes was completed in April, 1999. Many new cross-strait bridges were built between islands with beautiful natural environment of the Seto Inland Sea. Because of the number and scale of these bridges, concerns were expressed about their impact on the natural environment in the area, Especially, highway lights are installed high up on the bridges. They cut across open spaces above the straits, which are important for the flight of birds. It has been pointed out that the bridge illumination could affect in various ways the lives and behaviors of birds who depend heavily on their sense of vision. The purpose of this study is to conduct surveys on the species and number of birds in the area over a period of eight years, and to assess the influence of the illumination of cross-straits long bridges on the surrounding nature. The survey stations were set up at both ends of the Shimotui-Seto Bridge on one of the three Honshu-Shikoku Bridge Routes and the changes in the number of birds species and the number of individuals had been traced. The result of the survey indicates that no apparent changes were incurred by the illumination apparatus on the long marine bridges. However, it is recommended that periodical and long-term observation of birds are continued, and that the survey should be conducted not only on the daytime but also on the nighttime migration of birds.