Fig-eating and seed dispersal by birds in a Malaysian lowland rain forest
This study investigates avian fig-eating and Ficus seed dispersal in a patch of lowland rainforest at Kuala Lompat, Peninsular Malaysia, in the period March 1984 to April 1987.Of 38 Ficus species identified in c.2 km2 of forest, 29 possessed seeds primarily dispersed by birds. A phenological study of these species showed that figs were available in every month, and that the Ficus community exhibited distinct aseasonal fruiting rhythms. Nevertheless, crops of large figs (>25mm mean dimension) were rare, with only 13--16 large-fruited fig-patches per km2 of forest per year. The 60 bird species which ate figs at Kaula Lompat partitioned the fig resource according to fruit size, even though the soft nature of figs enabled birds of all sizes to feed on figs of all sizes. All birds, except some pigeons, rapidly defaecated ingested Ficus seeds. Treron pigeons were specialised fig-seed predators, and were found to eat large proportions of some fig crops; c.30% in one studied fruiting. Radiotracking and observations of foraging birds showed that many species stayed close to large fruit patches. As a consequence of this behaviour, and rapid gut-passage rates for Ficus seeds, seed shadows of bird-dispersed Ficus are anticipated to be leptokurtic. The most important Ficus seed dispersal agents, in terms of long distance dispersal, are predicted to be the larger, specialised frugivorous birds. Bird-dispersed Ficus at Kuala Lompat were all epiphytic species, growing predominantly on large commercial timber trees. Selective logging of lowland forest is therefore predicted to severely deplete the density of bird-dispersed Ficus, especially those species with large figs. Birds particularly dependent on such figs, such as Treron capellei and some of the hornbills, are severely threatened by such practices. Recommendations are made to promote the survival of these vulnerable bird species.