Assessing potential Argentine Ant recruitment to pipping eggs in the Red-tailed Tropicbird on Rapa Nui (Easter Island)

Abstract

ABSTRACTThe invasive Argentine Ant, Linepithema humile, is known to prey on land bird chicks, but there are few reports of the ants’ impacts on breeding seabirds. We conducted a manipulative study using hen eggs to estimate the potential Argentine Ant recruitment to pipping eggs in the Red-tailed Tropicbird, Phaethon rubricauda, at Rapa Nui (Easter Island), Chile. Hen eggs were experimentally opened to simulate pipping eggs and control eggs were left unopened. The eggs were monitored for 90 min. The time elapsed until the arrival of the first ant did not differ between experimental and control eggs. None of the control eggs were visited by more than two ants. In contrast, the inferred cumulative number of ants that arrived at experimental eggs varied from 1 to >450. Simulated pipping eggs attracted a high number of ants in a short period of time, and the probability of an egg being attacked by ants after 5 and 60 min of exposure was 75% and 99%, respectively. A long-term monitoring study is needed to determine the actual Argentine Ant recruitment rate on pipping eggs, and the potential effects on the post-fledging survival rate of this native seabird which is threatened by a number of introduced species.