Wintering grounds under protection: population stability and conservation of migrating waders at Europa Island, western Indian Ocean

Abstract

The tropical western Indian Ocean islands are at the southern limit of the East Africa–West Asia Flyway, but their importance for wintering and conservation of Palearctic waders remains poorly understood. Europa Island, a remote coralline island in the southern Mozambique Channel, is a Ramsar site administered since 2005 and managed since 2007 by the Terres australes et antarctiques françaises (TAAF). Although the island is best known for its important seabird assemblages, its importance as a major breeding site for green turtles, and for its native vegetation and undisturbed coral reefs, it also supports a variety of migratory waders from the Palearctic. However, their abundance, seasonal changes in numbers, and trends are poorly documented. This study, conducted from 2016 to 2024, presents the results of monthly and bimonthly wader censuses. Twenty-one species of waders were observed during this period, where the Ruddy Turnstone Arenaria interpres, Eurasian Whimbrel Numenius phaeopus, Grey Plover Pluvialis squatarola, Greater Sand Plover Anarhynchus leschenaultii and Common Greenshank Tringa nebularia were the most abundant. Peak numbers averaged 667 ± 103 individuals (range: 557–850) annually, with the central lagoon serving as the principal habitat (593 birds on average during peak months with a range of 194–885). The airstrip was the second most important site, with an average of 443 birds (range: 317–646), the most abundant species being the Ruddy Turnstone, with an average of 432 ± 110 individuals during peak periods. The wintering period of most species was between September and March, with some interspecific variations. Trend analysis indicated stable wader populations over the study period. Furthermore, the average numbers were comparable to counts made in the early 1990s, suggesting a long-term stability. These findings highlight the importance of Europa as a wintering site for palearctic waders in the western Indian Ocean despite its small size and remoteness.