Grey seals in the Wadden Sea National Park of Lower Saxony Winter/Spring 2006/2007 (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.为更精准地掌握野外种群的实际状况，国家公园管理局（National Park Administration）会在冬季与春季开展专项航空调查飞行。冬季为灰海豹幼崽的降生时期，春季则迎来其一年一度的毛皮换发阶段——这两个生命阶段均为陆上灰海豹的种群计数提供了极佳契机。