Frugivory by birds on two subtropical dry forest tree species (Almacigo Bursera simaruba and Guayacan Guaiacum officinale) in Guanica, Puerto Rico

I studied the frugivory activity of birds in two dry forest plant species of the Guanica Forest in Puerto Rico. The two plant species are Almacigo Bursera simaruba and Guayacan Guaiacum officinale . I examined how traits present in both plant species relate to the two seed-dispersal models proposed by others. Model I predicts that Guaiacum have an extended fruiting season with a very high rich-nutrient fruit (high in lipids) production that attract a smaller assembly of large bird dispersers (specialists). In contrast, model II predicts that Bursera have a short-peaked fruiting season of a lower nutrient-poor (high in lipids) fruit production which attract a large assembly of smaller bird dispersers (opportunists). I also examined frugivory by birds on other plant species in the Guanica Forest.;Bursera simaruba exhibited an extended fruiting phenology and Guaiacum officinale exhibited a short-peaked fruiting season. This is inconsistent with the prediction in the seed-dispersal models. Annual fruit production was significantly higher in Bursera simaruba than in Guaiacum officinale. This is consistent with the seed-dispersal models.;I observed nine frugivorous bird species feeding on Bursera, whereas only two large bird species were observed feeding on Guaiacum . This is consistent with the predictions in the seed-dispersal models. The number of visits by frugivorous birds was significantly higher in Bursera than in Guaiacum. This also supports the prediction proposed by the models. Both bird species visiting Guaiacum are considered opportunists feeders on a number of plant species. This partially opposes the model since the birds do not exclusively depend on Guaiacum fruits.;Bursera simaruba fruits contain more water, sugar, and protein, than Guaiacum officinale. The latter had a significantly higher amount of lipids. However, the total metabolizable energy offered by both fruits was not significantly different.;For the most part there is a dichotomy of plant traits consistent with both of the proposed seed-dispersal models. However, fruiting seasonality is an exception. Rainfall might be influencing such traits in both plant species. Bursera simaruba potentially receives better dispersal services than Guaiacum officinale. In addition, the study supports the idea that fleshy fruits are quite abundant in dry forests and some birds recognized as primarily insectivorous are, in fact, very dependent on fruits. Thus, the study strongly suggests that seed-dispersal in dry forest ecosystems is as important as other studies have shown for wet or rain forests. I conclude that the management and conservation decisions for such ecosystems should include at least general knowledge of the seed-dispersal relationships. (Abstract shortened by UMI.).