Recovery of insular seabird populations years after rodent eradication

Abstract

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 posteradication surveys to decipher the mechanisms of seabird recovery and confirm the benefits of eradication for conservation purposes.

Tracing the fate of seabird‐derived nitrogen in a coral reef using nitrate and coral skeleton nitrogen isotopes

“…Surprise Atoll's coral reefs host benthic coral assemblages dominated by scleractinian species (Wantiez et al 2022). Covered with bushes and small trees, Surprise Island is a refuge for about 13 breeding marine seabird species accounting for more than 14,000 breeding pairs of epigeous species (Supporting Information Table S1; Thibault et al 2022; Philippe‐Lesaffre et al 2023). The surrounding seawater has low nutrient concentrations (< 0.5 μ M of ), typical of the oligotrophic waters of the Coral Sea (Bonnet et al 2015).…”

FrigatebirdsFregata: impacts of potential taxonomic change on population and conservation status

“…Australian populations appear stable (but few data after the 1980s); apparently increasing on Cocos (Keeling) Is (James and McAllan 2014), but a recent count of 711 nests (Clarke et al 2021 unpublished report) would not seem to support this. The combined populations of F. a. ariel and F. m. minor at Surprise I., d’Entrecasteaux Reefs (New Caledonia) increased from 398 pairs (1996) and c.150 pairs (2002–2005) to 1,586 pairs in 2017, following a successful rodent eradication in 2005 (Philippe-Lesaffre et al 2023).…”

“…The combined populations of F. a. ariel and F. m. minor at Surprise I. (d’Entrecasteaux Reefs, New Caledonia) increased from 398 pairs (1996) and c.150 pairs (2002–2005) to 1,586 pairs in 2017, following a successful rodent eradication in 2005 (Philippe-Lesaffre et al 2023).…”

“…Data sufficiently reliable to infer population change are available for very few sites. Multi-year regular monitoring studies of frigatebirds seem even fewer; the only recent/current ones identified were Baker and Holdsworth (2013) and Philippe-Lesaffre et al (2023).…”

“…Thus, the combined breeding populations of F. ariel and F. minor at Surprise I. (New Caledonia) increased from c.150 pairs in 2002–2005 to 1,586 pairs in 2017, following a successful rat eradication in 2005 (Philippe-Lesaffre et al 2023). Similarly, at Howland, Jarvis, and Baker islands (US Minor Outlying Is) populations increased from actual or virtual elimination by the 1980s to a combined maximum of c.24,000 birds of F. ariel and 3,850 birds of F. minor by 2002–2007, following successful cat eradications by 1990 (Rauzon et al 2011).…”