鄱阳湖4种鹤类集群特征与成幼组成的时空变化

Temporal and spatial variations in the group characteristics and adult-juvenile composition of four crane species in Poyang Lake,China

2014年10月—2015年4月,采用样点法对鄱阳湖45个样点的白鹤(Grus leucogeranus)、白头鹤(G.monacha)、白枕鹤(G.vipio)和灰鹤(G.grus)的集群大小、集群类型和成幼组成进行调查。结果显示,白鹤的平均集群大小(23.86±10.26)只(集群数N=104),白头鹤(6.42±1.63)只(N=98),白枕鹤(6.09±2.55)只(N=105),灰鹤(5.55±1.26)只(N=246)。仅白头鹤中期集群大小显著小于后期,其余鹤类各时期及灰鹤各地区的集群大小差异不显著。鄱阳湖鹤类的集群大小并不符合警戒行为对集群大小的预测,生境质量差异可能是影响鄱阳湖鹤类集群大小的主要原因之一。4种鹤类均在1—5只个体的小集群中出现频度最高。白鹤在>35只个体集群中的个体比例最高,而白头鹤、白枕鹤和灰鹤在1—5只个体集群和>35只个体集群均有较高的个体比例。白鹤、白头鹤、白枕鹤和灰鹤均以家庭群为主,其家庭群所占比例分别为(64.29%,总集群数N=98)、(71.91%,N=89)、(70.77%,N=65)和(63.11%,N=206)。鄱阳湖鹤类以家庭群为主表明,保证充足的食物供应可能比花费更多的觅食时间更为重要。白鹤家庭群以2成1幼为主(65.08%),白头鹤(51.56%)、白枕鹤(52.17%)和灰鹤(47.69%)以2成为主。白鹤、白头鹤、白枕鹤和灰鹤群体的幼鸟比例分别为12.27%(个体数N=1695)、14.42%(N=416)、16.59%(N=229)和20.46%(N=655)。2成2幼集群比例极低表明,白鹤家庭同时抚养2个幼鸟成活的难度较其它3种鹤类大。4种鹤类在各时期的幼鸟比例差异不显著。在灰鹤个体数较多的3个地区中,都昌候鸟省级自然保护区(25.25%)和东鄱阳湖国家级湿地公园(25.14%)的幼鸟比例分别显著和极显著地高于鄱阳湖国家级自然保护区(14.24%)。鄱阳湖白鹤的幼鸟比例多年来均处于较低水平,白头鹤的幼鸟比例较2012—2013年冬季明显下降,灰鹤和白枕鹤种群可能处于稳定或增长状态。

Poyang Lake is the largest freshwater lake in China, and many waterbirds, including four endangered crane species, overwinter at this lake each year. Feeding and resting are the behaviors primarily exhibited by the wintering waterbirds, that Poyang Lake provides good food and rest resources for them. However, no comprehensive data about the wintering ecology of these crane species exists. From October 2014 to April 2015, we investigated the group sizes and adultjuvenile compositions of the Siberian crane （ Grus leucogeranus）, hooded crane （ G. monacha ）, white-naped crane （ G. vipio）, and common crane （G. grus） at 45 survey sites on Poyang Lake using the point count method. The results showed that the mean group sizes of the four crane species were （23.86±10.26） for the Siberian crane （group number N= 104）, （6.09±2.55） for the hooded crane （N=98）, （6.09±2.55） for the white-naped crane （N= 105）, and （5.55±1.26） for the common crane （N= 246）. Crane group size in Poyang Lake did not conform to predictions based on their vigilance behavior. However, habitat quality may explain this discrepancy. The group size of hooded cranes at the mid-winter stage was significantly smaller than during the late winter stage, whereas other cranes showed no significant differences between the three wintering stages. The common crane group size also showed no signifieant differences between regions. The four species of cranes most frequently appeared in groups of 1-5 individuals. Most Siberian crane individuals appeared in groups of 35 individuals or more, whereas other cranes were in groups of 1-5, or more than 35 individuals. The Siberian crane （64.29%, total group number N = 98） , hooded crane （71.91%, N = 89） , white-naped crane （ 70.77%, N = 65 ） , and eommon crane （63.11%, N= 206） appeared mainly in family groups, suggesting that ensuring an adequate supply of food was more important than increasing foraging time. The highest percentage of Siberian crane family group types was two adults with one offspring （65.08%）, whilst two adults predominated in the hooded erane（51.56%）, white-naped crane （52.17%）, and common crane （47.69%） populations. The lower percentage of family types with two adults and two offspring indicated that Siberian erane families found it more difficult than the families of the other three cranes to raise two offspring at the same time. The percentage of juvenile Siberian cranes was 12.27% （individual number N= 1695） , 14.42% （N= 416） for the hooded crane, 16.59% （N = 229） for the white-naped crane, and 20.46% （N = 655） for the common crane. There was no significant difference in the percentage of juveniles over the three wintering stages for any of the crane species. Duehang Provincial Migratory Birds Nature Reserve and East Poyang Lake National Wetland Park were found to contain significantly and extremely signifieantly （~2= 6.495, P = 0.011 and Xz= 9.012, P = 0.003, respectively） more common cranes （25.25% and 25.14%, respectively） than Poyang Lake National Nature Reserve （14.24%）. The percentage of juvenile Siberian cranes remained low in Poyang Lake, whereas that of the hooded eranes significantly decreased between 2014 and 2015 from the corresponding percentage of the population in 2012-13. The population of common cranes and white-naped cranes remained stable or inereased, which suggested that Poyang Lake is able to maintain and develop healthy populations of these cranes.