The effect of artificial perches and local vegetation on bird-dispersed seed deposition into regenerating sites

ABSTRACT: Knowledge of the role of birds in natural regeneration could be used to accelerate and reduce the costs of forest restoration. This study determined: (1) whether artificial bird perches, placed in sites at various stages of natural and human-assisted regeneration, increased seed deposition, and (2) which local vegetation features influence input of bird-dispersed seeds. The seed rain, under perches on six plots located in two different sites in northern Thailand, was examined. One site contained three naturally regenerating plots, ranging from nearly treeless and grass-dominated to > 25% shrub cover. The second site contained three, one-year old experimental forest restoration plots.

The species richness and density of bird-dispersed seeds were significantly higher below perches than at control points at both sites. After seven months, seed input under the perches was greatest at a restoration plot that contained two fruiting trees, Debregeasia longifolia and Clerodendrum glandulosum, which were regularly visited by at least five bird species. However, the median input of bird-dispersed seeds was significantly higher on the three naturally regenerating plots (13.5 versus 0 seeds/trap). Total species richness of birds visiting perches was also higher on the naturally regenerating plots (15 versus 8 species). Although landscape variables have not been quantified, all of the naturally regenerating plots were closer to remaining forest patches compared to the restoration plots.

Our preliminary results suggest that perches offer a useful technique for potentially increasing seed deposition by birds. Our circumstantial evidence also suggests that, in the absence of nearby forest, the presence and specific characteristics of fruiting trees used for restoration plantations can have a significant impact on the ability of plantations to attract seed-dispersing birds.