Oriental Turtle-dove
Streptopelia orientalis

The Oriental Turtle-dove is found across much of east Asia and Siberia, with Northern populations being migratory. They are found year-round in Japan and birds there are race orientalis, occurring in a range of habitats from woodlands and famrs to city parks. They are fairly small doves at 33-35 cm in length.
 

1: Mt Takao, 24/05/2012.
2: Ueno Park, Tokyo, 17/05/2012.