北京地区居留黑鹳的越冬生态学

由于气温的变化,原来属于夏季繁殖鸟的国家一级保护鸟类黑鹳(Ciconia nigra),在北京市出现了越冬群体.为了解黑鹳的越冬生态特点,从2004年1月到2009年3月,在北京十渡水生动物自然保护区,对其种群数量、生境选择、取食规律和集群行为进行了实地调查.结果显示,黑鹳选择该保护区的拒马河作为其越冬地,种群数量从2004-2005年冬季的28只下降到2007-2008年的17只,但随后恢复到了23只.越冬群体于11月中旬形成,次年3月中旬分散,但群体形成受到温度变化的影响.黑鹳对取食生境具有依赖性,主要食物为鱼类(＞92.4%).成年和亚成年黑鹳的食物构成没有差异(Mann-Whitney Utest,U=1.00,p=0.44).在越冬初期,取食活动主要发生在早晨和中午,越冬中期则集中于下午,而在越冬后期,分为清晨和傍晚两个取食阶段.按照每日取食6 h计算,成年黑鹳的每日进食量约538 g,亚成年个体约449 g,与人工饲养条件下黑鹳的饲喂量相近.在越冬后期,观察到取食过程中群体内部存在争斗行为.对越冬黑鹳的干扰主要来自旅游活动对取食生境的改变、人为筑坝提高水位、在滩涂开辟新的旅游场地减少了适于黑鹳取食的空间.

Wintering ecology of the Black Stork (Ciconia nigra)in Beijing

The Black Stork (Ciconia nigra) is a new winter resident in Beijing due to temperature changes.To understand the wintering ecology of this species better, a field survey covering the number of birds of this population, habitat selection, feeding activity and grouping behavior was conducted at the Shidu Nature Reserve from January 2004 to March 2009. The results show that the Black Stork selected the Juma River at this nature reserve as their new winter habitat. The number of birds in this population decreased from 28 in the 2004/2005 winter to 17 in the 2007/2008 winter with a subsequent recovery to 23 the following year. The wintering flock was formed in mid-November and dispersed in mid-March, but the date changed with seasonal temperature fluctuations. The storks exhibited feeding habitat fidelity and the main food type was fish (＞ 92.4%). There was no significant variation in food composition between adults and sub-adults (Mann-Whitney U test, U = 1.00, p = 0.44). Feeding activity occurred in the morning and at noon during early winter, but concentrated in the afternoon during mid winter, divided into dawn and dusk in late winter. Daily fish intake was 538 g for adults and 449 g for sub-adults if the period of foraging reached six hours in the wild, which was similar to the level under artificial feeding. Agonistic behavior among feeding birds was observed among group members in late winter. The main negative factor for wintering Black Stork was a reduced feeding habitat resulting from increased water depth due to damming of the river to benefit tourism and to wetland exploitation.