Go your own way: avoidance and competitive exclusion by two Hawaiian honeycreepers at a critically imperiled aster

Abstract Within invasive dominated ecosystems, competitive exclusion, wherein one species prevents another from accessing a resource due to competition for overlapping niches, is typically understood in the context of native-invasive interactions. However, competitive exclusion may also be understood in the context of native-native interactions, where a subordinate species. varies either spatially or temporally from the dominant species to access resources not currently exploited by the dominant species. In ecosystems where native species are imperiled, it is of increased importance that the potential for these exclusions is understood. On the island of Oʻahu, the Oʻahu ʻamakihi ( Chlorodrepanis flava ) and the ʻapapane ( Himatione sanguinea ) are two birds native to the islands that may both serve as pollinators for imperiled plants. Using game cameras to monitor behavior at the endangered Hesperomannia oahuesnsis (Asteracaea), and by selective use of playback, we found that the dominant ʻapapane alters foraging timing of the subordinate ʻamakihi, with the latter delaying visits to the flower and shifting peak activity at the flower. However, ʻamakihi did not influence the behavior of ʻapapane. Taken together, these results show that, in invasive dominated ecosystems, competitive exclusion is not limited to native-invasive interactions, and must be taken into account when working to preserve multiple endangered species that occupy similar foraging niches.