Data from: Pre-laying movements of Yelkouan Shearwaters (Puffinus yelkouan) in the Central Mediterranean [2012-2014]

The pre-laying exodus (PLE) is considered a crucial period in the breeding biology of Procellariiformes as it determines the success of egg production within a season and, therefore, a population’s reproductive output. However, it has scarcely been studied compared to other stages of the annual cycle. Here we present the first pre-laying tracks of the vulnerable Yelkouan Shearwater (Puffinus yelkouan) through the Global Positioning System tracking of birds breeding on the Maltese islands in the Central Mediterranean, and compare PLE core utilisation areas to known areas used during the chick-rearing period. Females spend, on average, 13 days foraging during egg development, reaching an average maximum distance of 325.5 km from their breeding colony to forage at offshore areas mainly south of the Maltese islands; these journeys are of longer duration and cover a greater distance than those undertaken by males, and by females that are not developing an egg, during the same period. There is little to no overlap between the PLE core utilisation areas and those used during chick-rearing by the same populations. This confirms our expectations that the PLE differs from foraging trips undertaken outside of the egg development period. Our results highlight the need for more research into the factors attracting egg-producing females to the PLE foraging areas and the importance of trans-boundary marine protection for the conservation of vulnerable seabirds.

产卵前迁徙（pre-laying exodus, PLE）被视为鹱形目（Procellariiformes）繁殖生物学的关键时期，其直接决定单季产卵成功率，进而影响种群的繁殖产出。然而相较于年度周期内的其他阶段，该时期的相关研究仍较为匮乏。本研究首次通过对地中海中部马耳他群岛繁殖种群的全球定位系统（Global Positioning System, GPS）追踪，获取了易危（vulnerable）物种耶尔库剪水鹱（Yelkouan Shearwater, *Puffinus yelkouan*）的产卵前迁徙轨迹，并将该时期的核心利用区域与育雏阶段的已知活动区域进行了对比。雌性个体在卵发育阶段平均耗时13天开展觅食活动，最远可达繁殖群落以南325.5公里的近海区域觅食；此类觅食旅程的时长与覆盖范围均显著长于雄性个体，以及同期未处于卵发育阶段的雌性个体。产卵前迁徙的核心利用区域与同种群育雏阶段的活动区域几乎无重叠，这印证了我们的预期：产卵前迁徙与卵发育阶段之外的觅食行程存在显著差异。本研究结果凸显了针对吸引产卵雌性前往产卵前迁徙觅食区域的相关因素开展深入研究的必要性，同时也强调了跨界海洋保护对易危海鸟保育工作的重要意义。