Wide-ranging Movement and Foraging Strategy of the Critically Endangered Red-headed Wood Pigeon (Columba janthina nitens): Findings from a Remote Uninhabited Island

The Red-headed Wood Pigeon, Columba janthina nitens, is an endemic and endangered subspecies of the Ogasawara Islands. This pigeon moves irregularly among island habitats. However, its range and patterns of movement, particularly between the Bonin and the Volcano Islands, which are two remote island groups approximately 150 km apart, remain unclear. In this study, we conducted a survey on the uninhabited Kita-Iwojima Island of the Volcano Islands to collect direct evidence of pigeon movement between the two island groups and to reveal their food resource availability. Pigeon food composition was also analyzed. During the study period in Kita-Iwojima, we observed two individuals banded in Chichijima in the Bonin Islands. Food composition was estimated by fecal DNA analysis and compared with a fruit census of Kita-Iwojima, which differed from fruits observed in two monitored islands of the Bonin Islands, Chichijima and Hahajima. The pigeons might move among these islands to use available food resources, reflecting limitations of food resources in a single island habitat. Fruits detected in feces of the pigeons on Kita-Iwojima were not from plants observed on the island but rather derived from plants observed on Chichijima and Hahajima, likely indicating high movement capacity of pigeons among the islands. However, the foraging habitat of the Redheaded Wood Pigeon is limited to areas of low elevation in Kita-Iwojima despite apparent food sources at higher elevations. Therefore, factors beyond food abundance, such as geographical features, might affect habitat use of pigeons on the island.