Grey seals in the Wadden Sea National Park of Lower Saxony Winter/Spring 2010/2011 (UIG) Grey seals in the Wadden Sea National Park of Lower Saxony

In order to get a more accurate picture of the stock on site, the National Park Administration carries out special survey flights in winter and spring. In winter, the offspring is born and in spring, the annual fur change of the grey seals follows - both stages of life offer a good opportunity to count the animals on land.为更精准掌握现场种群的实际状况，国家公园管理局于冬季与春季开展专项航拍调查。冬季为灰海豹幼崽的诞生期，春季则迎来灰海豹一年一度的换毛阶段——这两个生命阶段均为统计陆地栖息的灰海豹数量提供了绝佳契机。