Abstract
Japanese White Eyes Zosterops japonicus were observed foraging on the nectar of Golden Trumpet Trees Tabebuia chrysotricha in Okinawa Island. Rather than accessing nectar from the opening of the flower, the white-eyes mainly robbed nectar by creating a hole at the base of the flower. They probably robbed nectar because their bills were too short to reach deeply into the long flowers. They perched on branches as they foraged, which also hindered them from getting at nectar from the opening of the flower. They did not appear proficient at hovering in flight, which would have allowed them better access to the flower opening.Robbing behavior included two methods. One was to insert the bill between petal and calyx. The other was to tear the petals. The latter type seemed to allow the reproductive organs to touch the bird's bill, which may assist pollination. In both maximum and average values, sugar concentration of Golden Trumpet Tree was higher than either Hibiscus Hibiscus rosa-sinens or Taiwan Cherry Cerasus campanulata. Golden Trumpet Tree would appear to be a potentially important food resource, but naturally-occurring naphthoquinone and phenolic glycoside may cause white-eyes to avoid this plant. Although the nectar robbing was frequently observed in 2011, we saw no case in 2012, 2013 and 2014.
