Benefits to the germination of seeds provided by birds that mandibulate fleshy fruits

Abstract

The effect of fruit removal and passage through the digestive tract of frugivorous birds on seed germination has been mostly studied in species that swallow the whole fruit without mandibulating (“gulpers”), and defecate or regurgitate seeds without pulp away from the maternal plant. Functional groups with other fruit-handling methods, while often quantitatively important in removing fruits, are presumed to provide lower quality seed dispersal due to their tendency to damage seeds with the beak or discard seeds with pulp still attached under the maternal plant. We conducted a series of experiments with five bird species that mandibulate fruits with the beak before swallowing (“mashers”). They were fed with fruits of one to five plant species to test the effect of handling on their germination. We compared germination probabilities and times of seeds defecated or dropped from the bill with seeds with pulp removed by hand. Overall, bird processed seeds germinated in equal proportions than manually extracted seeds (69.9 vs 70.2%, respectively). However, depending on the bird-fruit species pair considered, the proportion and germination time of seeds processed by masher birds were equal to or less than those of manually extracted seeds. Most of the retrieved seeds processed by these birds were defecated (94%), and a large percentage of them germinated (70.3%), which confirms that they are important for the seed dispersal process. Our results provide new insights on aspects of the qualitative component of seed dispersal by masher birds. We discuss the possible implications of these findings on seed dispersal in the rest of the Neotropical region.