Justification of Red List Category
This species is classified as Near Threatened because it has a small and declining range, which is not considered to be severely fragmented, and probably has a moderately small population, which is thought to be declining as a result of hunting and logging.
The global population size has not been quantified, but the species is described as uncommon (Gibbs et al. 2001).
There are no data on population trends; however, the species is suspected to be in decline owing to habitat degradation and hunting.
Columba janthina is an uncommon and local resident in Japan, on small islands off southern Honshu, Shikoku and Kyushu, south through the Nansei Shoto islands to the Yaeyama Islands and the Izu Islands to the Ogasawara and Iwo Islands (BirdLife International 2001). It occurs locally on small islands off the south coast of South Korea, and it has been recorded (presumably as a vagrant) in eastern Russia, Shandong, mainland China and Taiwan (China). Although it is still relatively common on the Izu Islands, it has apparently declined there since the 1950s, and it is thought to have declined on Okinawa during the 1980s because of forestry activities. There are estimated to be only 30-40 individuals of subspecies nitens on the Ogasawara Islands, but the status of this subspecies on the Iwo Islands remains unknown (per Otani Chikara in litt. 2005, Simba Chan in litt. 2005).
This species inhabits dense subtropical forest and warm temperate evergreen broadleaved forests, and is heavily dependent on mature forest. It feeds mainly on Camellia seeds, but is thought to take the seeds and fruit of other plants, and although it is mainly arboreal it will also take fallen seeds from the ground (Gibbs et al. 2001). Diet analysis of the subspecies Columba janthina nitens shows seasonal variation and the consumption of both native and introduced plant species (Ando et al. 2013, Ando et al. 2016). Breeding occurs from February to September, and females lay a single egg in a tree-hole or amongst rocks (Gibbs et al. 2001).
It is thought that hunting and deforestation are causing this pigeon to rapidly decline.
Conservation Actions Underway
There is a small captive population of subspecies nitens at Ueno Zoo, Tokyo, where successful breeding has occurred as part of a conservation programme (Otani Chikara in litt. 2005). Research into the genetic structure of the subspecies nitens suggests increased genetic diversity is needed in the captive population (Ando et al. 2014) Efforts to control cats within this species range could be benefitting this species.
Text account compilers
Benstead, P., Mahood, S., Taylor, J., North, A., Martin, R
Otani, C., Mizuta, T., Chan, S.
BirdLife International (2019) Species factsheet: Columba janthina. Downloaded from http://www.birdlife.org on 08/12/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 08/12/2019.