DIFFERENT PREY RESOURCES SUGGEST LITTLE COMPETITION BETWEEN NON-NATIVE FROGS AND INSECTIVOROUS BIRDS DESPITE ISOTOPIC NICHE OVERLAP

Robyn L Smith; Janelle Nolan & Associates Environmental Consulting; robyn@jna-consulting.com; Karen H. Beard, Aaron B. Shiels

The Puerto Rican coqui frog (Eleutherodactylus coqui) has colonized the island of Hawaii, and has been hypothesized to compete with insectivorous birds and bats. To address if the coqui could compete with these vertebrates, we used stable isotope analyses to compare the trophic position and isotopic niche overlap between the coqui, three insectivorous bird species, and the Hawaiian hoary bat. Coquis shared similar trophic position to Hawaii amakihi, Japanese white-eye, and red-billed leiothrix. Coquis were about 3‰ less enriched in ?15N than the Hawaiian hoary bat, suggesting the bats feed at a higher trophic level than coquis. Analyses of potential diet sources between coquis and each of the three bird species indicate that there was more dietary overlap between bird species than any of the birds and the coqui. Results suggest that Acari, Amphipoda, and Blattodea made up >90% of coqui diet, while Araneae made up only 2% of coqui diet, but approximately 25% of amakihi and white-eye diet. Results suggest that coquis share few food resources with insectivorous birds, but occupy a similar trophic position, which could indicate weak competition. Future research should examine whether coqui invasions are associated with changes in bird abundance.

Poster Session  InPerson Presentation