Work

Individual migratory patterns of the critically endangered Balearic shearwater: A multi-colony and multi-year study in the NE Atlantic

Year: 2025

Type: article

Abstract: Understanding the migratory patterns of declining species is essential to guide spatial conservation efforts. We studied the migratory dynamics of the Critically Endangered Balearic shearwater (Puffinus mauretanicus) by collecting biologging data from 88 annual cycles (53 individuals) between 2017 and 2022. Birds were tagged in three different colonies from the main islands (Eivissa, Mallorca and Menorca). We examined the non-breeding periods in the NE Atlantic, where the species migrates after breeding in the Mediterranean. Of all annual cycles, all birds from Eivissa and Mallorca migrated to the Atlantic (n = 78), whereas 80% of the birds from Menorca stayed in the Mediterranean (n = 10). Within the Atlantic, 54% and 41% of the main areas of the annual cycles were located in the Bay of Biscay and the Western Iberian Peninsula, respectively. Additionally, emerging individual variability highlighted the Gulf of Cádiz as an additional main area corresponding to the 5% of annual cycles. Regarding spatial consistency, 27 individuals carried geolocators for two or more consecutive non-breeding periods, of which 81.5% visited the same area annually. Time spent in each main area varied from 1 to 7 months. Earlier arrival to the main area correlated with a longer stay. The timing of outbound migration was influenced by breeding success: failed breeders entered the Atlantic a month earlier (median date = 25th May ± 20.4 days) compared to successful breeders (median date = 30th June ± 22.7 days). These results underscore the importance of long-term monitoring programmes to capture individual variability, made possible through biologging technology, in conserving declining species.

Source: Global Ecology and Conservation

DOI: 10.1016/j.gecco.2025.e03989