Recovery of insular seabird populations years after rodent eradication

Seabirds have been particularly affected by invasive alien species (IAS), which has led to the implementation of numerous eradication campaigns for the conservation of these keystone and highly vulnerable species. Although the benefits of IAS eradications for seabird conservation have been demonstrated, the recovery kinetics of different seabird populations on islands after eradication remains poorly evaluated. Here we present the results of an original long-term monitoring of the number of breeding pairs of seven seabird species on a small atoll, Surprise Island, New Caledonia (southwestern tropical Pacific). This long-term monitoring consists in a yearly core survey of the marine avifauna of the island conducted from 4 years before to 4 years after rodent eradication (conducted in 2005) combined with multiple one-time surveys from ∼10 years before and ∼15 years after eradication. This study was designed to evaluate how different seabird species responded to the eradication of invasive rodents in an insular environment. We found that three species responded positively to eradication with differences in lag-timing and sensitivity. The number of breeding pairs increased for two species in the four year post eradication due to immigration while one species showed a longer response time with an increase in pairs more than 10 years after eradication. Furthermore, we showed that long-term sampling is necessary to observe the responses of the seabird populations on the island. Our study confirms the positive effects of IAS eradication on seabirds and emphasizes both the importance of mid/long-term pre- and post-eradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes