Planting Design Effects on Avian Seed Dispersers in a Tropical Forest Restoration Experiment

Seed dispersal often limits tropical forest regeneration and animals disperse most rainforest tree seeds. This presents two important questions for restoration ecologists: (1) which animals are common seed dispersers? and (2) which restoration techniques attract them? Fourteen restoration sites were planted with four tree species in three designs, (1) controls (no planting, natural regeneration) (2) islands (trees planted in small patches), and (3) plantations (trees planted continuously over a large patch). We sampled birds in November, February, and April 2007-2008 with mist nets, in February and July 2009 with observations, and in July 2008 with both techniques. We documented 30 seed species from fecal samples of captured birds. All identified seed species were early-successional forms. Four tanager species, three thrushes, two saltators, two flycatchers, and one finch were categorized as common seed dispersers, based on their high likelihood of dispersing seeds. Common dispersers were generalist species with small gape widths (<15mm). Common dispersers were captured significantly more often in plantations than controls in most seasons and more often in plantations than islands during one season. Common disperser observations were significantly greater in plantations than controls during two periods and in plantations compared with islands in one period. Results indicate that plantation-style planting is the conservative strategy to maximize attractiveness to common dispersers in tropical restoration sites. Island planting is an alternative when resources are limited although disperser activity may be lower in some seasons than in plantations. Additional research should investigate how to attract large, forest-associated dispersers.