Number and distribution of cranes wintering at Poyang Lake,China during 2011-2012

Poyang Lake is a very important wintering place for cranes in China and East Asia.Two crane surveys were conducted at Poyang Lake during the 2011/2012 winter,the first on 18-19 December 2011 and the second on 18-19 February 2012.The survey covered the entire Poyang Lake basin,as well as two main lakes in Jiujiang (Saicheng Hu and Chi Hu),i.e.,a total of 85 sub-lakes were surveyed.Both surveys recorded four species of cranes.The first survey on 18-19 December 2011 recorded 4577 Siberian Cranes (Grus leucogeranus),mostly in Bang Hu,Sha Hu and Dahu Chi,302 Hooded Cranes (G.monacha),885 White-naped Cranes (G.vipio) and 8408 Eurasian Cranes (G.grus),for the most part in the center of the lake basin.The second survey on 18-19 February 2012 recorded 3335 Siberian Cranes (mostly in Poyang Lake National Nature Reserve (PLNR) and its surrounding areas),110 Hooded Cranes (largely in PLNR and its surrounding areas),283 White-naped Cranes (86％ in Bang Hu) and 2205 Eurasian Cranes (particularly in Duchang and Nanjishan NNR).The number of Siberian Cranes enumerated in December was 1000 more than the second count in February 2012.It is not possible to rule out double counting due to the close proximity of the main sites of the Siberian Cranes.During winters from 1998 to 2009,the average of the highest counts each winter was 3091,ranging from 2345 in 1996 to 4004 in 2002.By comparison with counts taken at other times,we therefore estimate a wintering population of Siberian Cranes of ～3800-4000 at Poyang Lake.Additional evidence will be needed to raise the world population estimate.Our more recent surveys indicate a continuing decline in the number of White-naped Cranes and an increase in Eurasian Cranes.

鄱阳湖沙湖越冬白鹤的数量分布及其与食物和水深的关系

为了摸清白鹤（Grus leucogeranus）的食物刺苦草（Vallisneria spinulosa）的资源状况和水深对白鹤活动的影响，于1999~2010年期间，对在鄱阳湖国家级自然保护区沙湖越冬的白鹤数量分布及其与食物刺苦草块茎和水深的关系进行了研究。在沙湖设置固定植物样线，每隔50～100m记录刺苦草及其块茎的数量和生物量，在视野能覆盖整个沙湖的制高点，定点观测白鹤的数量、分布和白鹤所处的水深。在这12a越冬期间，沙湖白鹤的多年总平均数量为46只，其中2002年、2006年和2009年冬季超过90只。11月至翌年1月是白鹤在沙湖比较稳定的时期，超过50只，其中12月是白鹤数量最多的月份，达到120只。白鹤在沙湖的中部偏南地带活动，北部和南端的数量很少。从栖息的植被带来看，白鹤几乎全部在以苦草（Vallisneria spp．）和眼子菜（Potamogeton spp．）为优势沉水植物的区域活动。沙湖刺苦草块茎的平均干重为5．92g／m2，2005年、2006年和2008年的干重接近或者超过12g／m2，2010年最少，仅为0．10g／m2。在1999-2010年期间，沙湖白鹤数量与刺苦草块茎干重不相关，隆冬12月至翌年1月的白鹤平均数量与刺苦草块茎干重的相关系数为r=0．231。在沙湖，有58．15％的白鹤在水深为5～27cm的环境中活动；其次，有30．63％的白鹤是在水深为40-45cm的环境中活动。而没有白鹤在旱地和水深及至腹部（46-50cm）的环境中活动。2010年鄱阳湖特大洪水对白鹤的影响比较大，发现有白鹤到草地上觅食的现象。