Inter-island movement of Japanese Wood Pigeons Columba janthina between Hachijo-jima and Hachijo-kojima in the Izu Islands

Abstract

We observed the inter-island movements of Japanese Wood Pigeons Columba janthina between Hachijo-jima and Hachijo-kojima in the Izu Islands on July 1, 2017. In total, about 2000 birds moved between the two islands during the 8 hours of observation. Average population density of C. janthina per 1 km of census line was much higher in Hachijo-kojima (69.93) than that in Hachijo-jima (1.54). Breeding behavior of C. janthina was also observed frequently in Hachijo-kojima, an uninhabited islet adjacent to Hachijo-jima, which seemed to be suitable breeding habitat for C. janthina because of its low degree of anthropogenic disturbance. On the other hand, due to the islet’s small size, it may be hard for C. janthina to obtain enough food resources on Hachjo-kojima. To augment the low food resources available on the smaller island, C. janthina may frequently move between Hachijo-jima and Hachijo-kojima.