UCB Moorea Class: Biology and Geomorphology of Tropical Islands

The study of systems containing multiple invasive species has long been superseded by the study of invasive impacts on native species. However, systems containing more than one invasive are likely to see the presence of ecological effects as a result of the relationships between those species. These effects are likely to be magnified in situations where invasives occupy similar niches. In this study I examine the foraging behaviors of two sympatric invasive bird species to determine if there is partitioning in either how, or where they forage. I also investigate their behavioral responses to the introduction of novel food stations, and natural fluctuations in foraging group size and species composition. Lastly I examine both their interspecific and intraspecific interactions. Results show that partitioning is present for both foraging behaviors and certain substrates being foraged on. Additionally, behavior at feeding stations trended towards foraging as opposed to vigilance. In conspecific groups, there were no behavioral changes observed with increasing group size in either species. However, the presence of heterospecifics was so rare, that no conclusions could be drawn about changes in foraging behavior for either species. Furthermore, intraspecific interactions were far more frequent, and of a greater agonistic intensity than interspecific interactions. These results imply that the two species are actively avoiding competition with each other, which contributes to both species being successful invasives.