| We investigated the effect of frugivorous birds on the seeds of Rosa Sericea, a dominant, fresh-fruited shrub in alpine environment of the Middle Reach of Yarlung Zangbo River. The fruits, which were important food for birds, ripened from late July through late August and persisted on the shrubs through the end of the year. July to October in 2003 and July to November 2004, I studied the birds foraging behavior on R. Sericea fruits to investigate frugivorous birds. To examine avian behavioral mechanisms of fruits selection, I measured the fruit characteristics and monitored the fruits dispersal ratio in different shrubs of the same plot and those in plots along altitudinal gradients. I also explored the seed rain and seedling dispersal pattern to understand the spatial of R. Sericea shrub recruitment. Five species of birds were found to consume the fruits of Rosa sericea, of which four were legitimate seed dispersers, one seed predator. Number of visits/ hour made by seed dispersers was significantly higher than those carried out by seed predator in all two years. Frugivorous birds aimed at ripe fruit and selected the fruits with more pulp. Dispersal efficiency (percentage of the fruit crop dispersed) correlated with crop size at the time. The fruits decreased firstly in lower height, and were dispersed more than 50% fruit crops in prime stage. The fruits of R. sericea did not have an extended fruiting season to slow fruit removal, and the dispersal peaks did not coincides with the fall migration season for migratory birds, the fruits removed mainly by all-year residents, but a trade-off might exist in dispersal attributes. The seed rain dispersal pattern was few seeds collected in open interspaces, under the shrub as a perch collected the higher seed densities. The seedling died for pressure of density, and the seedling distributed around shrub crown to obtain enough light and nutrition. That might give theoretical evidence for wildlife conservation in the area.
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