Seeds in droppings of tropical fruit-eating birds: importance of considering seed composition.

The probability of interspecific seedling competition from bird droppings is high because fruit-eating birds, on average, deposit more than two species in a single dropping. Moreover, birds vary both in the number of plant species they deposit in a given dropping and in the seed composition of those droppings. In a preliminary experiment, I examined effects of interspecific seedling competition from seeds found in bird droppings. Certain plant species were competitively superior in pairwise growth experiments using six common second-growth species. The survival of certain shrubs depended on which species it was disseminated with in bird droppings. Rapid germination time may promote competitive superiority in some cases. Birds affect plant fitness not only because of their behavior following dispersal, but also because they deposit seeds in different densities and combinations.