西藏南部羊卓雍错水鸟群落及斑头雁活动区域特征

2009年4月至2010年1月,对西藏南部羊卓雍错的水鸟资源状况进行了调查。采用定点观察的方法,沿湖选择了24个观察点,分别在繁殖前期、中期和后期,以及秋季和冬季进行了6次调查。采用核密度分析(Kernel analysis)的方法,对两只卫星跟踪斑头雁(Anser indicus)的活动区进行了分析。调查期间,记录到水鸟32种31044只,隶属于6目10科。雁鸭类和鸥类分别占水鸟总数73.9%和19.1%,主要是斑头雁、赤嘴潜鸭(Rhodonessa rufina)、赤麻鸭(Tadorna ferruginea)、棕头鸥(Larus brunnicephalus)等。水鸟多样性较高的季节是春秋迁徙季节。羊卓雍错夏季主要的繁殖种群是斑头雁和棕头鸥,也有少量黑颈鹤(Grus nigricollis)的繁殖个体;冬季主要物种是赤嘴潜鸭,经常聚集在融化的冰面上。春季斑头雁的数量增加趋势较为明显;进入繁殖期后,斑头雁处于孵卵阶段,繁殖种群的数量达到2000余只;繁殖后期,斑头雁换羽结束,成鸟带领幼鸟在鸟岛附近的湖边取食,此时观察到斑头雁的数量又有明显的增加;秋季斑头雁的南迁致使种群数量呈下降趋势;冬季许多斑头雁从北方如青海湖等地迁来越冬使得种群数量有所增加,多分布于湖西浪卡子县城附近的沼泽湿地和湖南部的绒波臧布河流的入口处。卫星跟踪结果表明,羊卓雍错是青海湖繁殖的斑头雁重要的越冬地之一,湖西部沼泽湿地和湖南部的河流入口处是其主要活动区域,而且该湖与雅鲁藏布江河谷之间通过斑头雁的往来移动存在着联系,因而是西藏南部禽流感监测的重要地点。

The water bird community and home range of the bar-headed goose at Yamdrok Lake in Tibet, China

From April 2009 to January 2010, we conducted surveys to determine the current status of water birds at Yamdrok Lake in Tibet, China. During the survey, visual search was the main method used. Twenty-four sites were selected around the lake, based on water bird distribution and accessibility by road. Once flocks were identified, observers approached the birds close enough on foot for identification and counting. The winter home ranges of two individuals of the bar-headed goose Anser indicus were by kernel analysis to determine the sites that were important for wintering of the bar-headed goose. A total 31,044 water birds were tallied, belonging to 32 species, 10 families, and 6 orders. Birds of the family Anatidae and gulls were predominant among the species counted, with proportions of 73.9% and 19.1%, respectively. The migration peaks of water birds at Yamdrok Lake occur in spring and autumn. Bar-headed geese and brown-headed gulls (Larus brunnicephalus), along with a small population of black-necked cranes (Grus nigricollis), occupied the major parts of the breeding grounds in summer, while the red-crested Pochard (Rhodonessa rufina) was the dominant species in winter, often resting in areas where ice was melting. The results also showed that population numbers of the bar-headed goose varied with season. Thus, its numbers increased slightly in spring, resulting from migration to the lake from southern populations, such as those from India. During the breeding period, over 2000 breeding individuals were recorded nesting at the bird island in the southwest part of the lake, and geese were seldom found in other areas. During molting, and with pressure from increasing populations, geese with their chicks were often seen foraging in the marshes and other wetlands along the edges of lakes. The population numbers decreased in autumn as many geese departed for their wintering sites. In winter, because of arrivals at the lake from northern areas such as Qinghai Lake and Qiantang, Tibet, the goose population increased again, and they were often found in the marshes and wetlands of the lake, where abundant food was available. According to the results from satellite tracking, Yamdrok Lake is an important wintering and breeding site for the bar-headed goose at Qinghai Lake, and the geese were often found in the marshes at the western end of the lake and the delta in the southern lake. In addition, a close link between Yamdrok Lake and the Yarlung Zangbo River benefitted the movement of the bar-headed goose between these two sites. As a result, it is reasonable to suggest that the lake should be seen as an important site at which to conduct surveillance in southern Tibet for avian influenza.