• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable (inferred from the absence of threats) thus does not qualify the species as threatened under the population trend criterion (>30% decline over three generations). The population size is unknown, but is not suspected to be sufficiently small to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The population has not been quantified and an exercise to do so would be greatly hampered by its movements between islands. On islands where the majority of tree cover has been removed it is expectedly rare, but on others it can be quite common (eBird 2022). The population of C. j. nitens has previously been estimated to number 100 in 2014 (Ando et al. 2014) however it is recently reported to be commoner following feral cat control (O. Chikara in litt. 2020).

Trend justification
While the number of recorded sites fell between atlas efforts in 1997-2000 and 2016-2021 (from 25 to 22) (Bird Breeding Distribution Survey Committee 2021) this is not thought to be indicative of global population declines. In the absence of hunting and logging pressures and recent indication that C. j. nitens (which can represent only a small percentage of the global population) is no longer decreasing thanks to conservation effort (O. Chikara in litt. 2022), the population is suspected to be stable.

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, recently thought to be commoner with the population recovering following feral cat control, albeit the status of this subspecies on the Iwo Islands remains unknown (O. Chikara in litt. 2005, S.Chan in litt. 2005, O. Chikara in litt. 2020).

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 (subspecies nitens is however more terrestrial; O. Chikara in litt. 2020) it will also take fallen seeds from the ground (Gibbs et al. 2001). Diet analysis of the subspecies 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). Subspecies nitens will breed from November, but may breed throughout the year (O. Chikara in litt. 2020).

In Japan, hunting and logging are not considered to be major threats (O. Chikara in litt. 2020). Humans settlement in the early 19th Century has lead to serious disturbance of habitat throughout the Ogasawara Islands (Ando et al. 2016). Introduced plants from tropical America and the Ryukyu Islands has moreover lead to loss of native fruits and plants, albeit the species is known to feed on non-native plants, possibly to compensate for the lack of native food (Ando et al. 2016)  and this is not considered a threat here. Feral cats have previously been an issue on Bonin Island (Ando et al. 2014) but recent control has positively impacted C. j. nitens.

Conservation Actions Underway
Research into the genetic structure of the subspecies nitens suggests increased genetic diversity is needed in the captive population (Ando et al. 2014). It is declared a National Monument across the Ogasawara Islands (Baptista et al. 2020).

Conservation Actions Proposed
Survey to assess population size. Regularly monitor to determine population trends. Investigate its tolerance of degraded forest and the extent of hunting by local residents. Control hunting where possible, perhaps using awareness campaigns. Protect significant areas of intact forest on a number of islands across its range. Conduct research into the taxonomic status of its subspecies. Investigate the status of subspecies nitens on the Iwo Islands. Monitor dependence on introduced plants, and the potential affect of introduced plant eradication programmes on foraging abilities (Ando et al. 2016). 

Text account compilers
Fernando, E., Berryman, A.

Contributors
Chan, S., Chikara, O., Mizuta, T., Taylor, J., Benstead, P., Martin, R., North, A. & Mahood, S.

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Recommended citation
BirdLife International (2024) Species factsheet: Japanese Woodpigeon Columba janthina. Downloaded from https://datazone.birdlife.org/species/factsheet/japanese-woodpigeon-columba-janthina on 22/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 22/12/2024.