Fruiting of fleshy-fruited plants and abundance of frugivorous birds: Phenological correspondence in a temperate forest in central Japan

Abstract

We investigated the seasonal correspondence between the fruiting phenology of fleshy-fruited plants and the abundance of frugivorous birds, in a temperate forest, in central Japan. The majority of fleshy fruits ripened in the fall when frugivorous birds were most abundant. This correspondence occurred earlier than in a warm temperate forest, located in southern Japan; these relationships in East Asia coincide with those of the temperate regions of North America and Europe. We also examined whether the abundance of frugivorous birds led to profitable effects for seed dispersal among fleshy-fruited plants. The Brown-eared Bulbul Hypsipetes amaurotis was considered to be an important seed disperser for many fleshy-fruited plants because of its high frequency of occurrence throughout the fruiting season, and its large gape size, which allowed it to swallow all sizes of fruits found at the study site. Although numerous Brown-eared Bulbuls and other frugivorous birds were present in the fall, fruit removal rates in fall-fruiting species were not always higher than in summer-fruiting species. The abundance of frugivorous birds alone could therefore not adequately explain the concentrated fruiting phenology among fleshy-fruited plants.