Columba janthina nitens is not extinct, but is treated as a endangered subspecies by Ministry of the Environment(2002).
Ministry of the Environment(2002) described as follows;
"Columa janthina nitens is one of three subspecies of C. janthina, a large wood pigeon endemic to Japan. This subspecies occurs only on the Bonin and the Volcano islands, where it feeds mainly on fruits in mature broad-leaved evergreen forest. The minimum population is estimated to be 30 to 40 birds. The reduction in the area of its forest habitat, coused by browsing by introduced goats, and human-related deforestation, is considered to be the major threat to this subspecies."
Reference:
Ministry of the Environment (ed.) 2002. Threatened Wildlife of Japan - Red Data Book 2nd ed.- Volume 2, Aves. Japan Wildlife Research Center, Tokyo.