黄河三角洲东方白鹳繁殖期觅食栖息地的利用

2008和2009年3—6月,在黄河三角洲自然保护区采用定点观察、GPS定位、样方调查和逐步判别分析等方法对东方白鹳(Ciconia boyciana)繁殖期觅食地的利用进行了研究。共测定了75个觅食利用样方和74个对照样方的14个生态因子。结果表明,东方白鹳繁殖期倾向于在明水面、芦苇沼泽和滩地中觅食,对草地和农田利用极少。偏向于食物丰富度较高的觅食点;对隐蔽级高低没有明显的偏好。对利用样方和对照样方进行比较,发现利用样方具有植被高度和植被盖度较低,觅食地水深相对较浅,距明水面、芦苇沼泽、树林等距离较近,距重度干扰源较远等特征。逐步判别分析表明,距芦苇沼泽距离、样方内水深、距重度干扰源距离、食物丰富度和明水面距离具有重要作用,由这5个变量构成的方程在对繁殖季节东方白鹳觅食地利用样方和对照样方进行区分时,正确判别率可以达到95.5%。东方白鹳繁殖期觅食地的利用主要与水源、人为干扰和食物条件有关。

Foraging habitat use of the oriental white stork during its breeding season

The oriental white stork (Ciconia boyciana) is one of the largest birds, with a wing span of up to two meters. Its breeding territory extends from the Amur to the Ussuri River in east Siberia, and 2500 individuals estimated still exist worldwide. According to the IUCN red list, however, the survival of this species is still in peril. Yellow River Estuary nature reserve had become their new breeding sites since 2005. From March to June in 2008 and 2009, the forage habitat use of Oriental white stork during its breeding season was studied in the Yellow River Estuary nature reserve by the methods of fixed-spot observation, GPS positioning, sampling plot investigation and stepwise discriminant analysis, by the methods of fixed-spot observation, GPS positioning, sampling plot investigation and stepwise discriminant analysis. With a forage site as the center, a 1m × 1m square quadrat was Set up, and another four square samples were installed of 5-10 miles around the first square quadrat. Based on the previous research methods and the actual situation, 14 ecological factors were determined as follows: vegetation type, vegetation height, vegetation density, vegetation coverage, sheltering class, water depth in quadrat, the distance to water, the distance to the reed marsh, the distance to the serious disturbance, the distance to the mild disturbance, the distance to grassland, the distance to forests, distance to nest and the distance to farmland. In order to ensure the randomness of quadrats the study area will be divided into 256 areas with equal or similar size, in which the quadrat must be covered. If the Oriental white stork foraged within the quadrats, this quadrat would be removed. A total of 75 foraging and 74 random plots were measured and analyzed in each site. The Oriental white stork preferred water depth of about 20cm, the reed marsh and the beach, while they avoided grassland and farmland. Comparing the used sites with the random plots, the used sites were characterized by lower vegetation height and density, lower water depth, shorter distance to water source, the reed marsh and forests, farther to the serious disturbance, and more abundance of food. Nine ecological factors which had significant difference were analyzed using Spearman''s rank correlation test, and the correlation coefficients were less than 0.6. Stepwise discriminant analysis indicated that distance to the reed marsh, water depth in quadrat, distance to the serious disturbance, distance to the serious disturbance, food abundance, distance to water were critically factors to discriminate foraging sites and random plots. The overall classification model developed from five variables was successful to distinguish the used sites from random ones at probability of 95. 5%. Water, human disturbance and food are main factors which affect foraging habitat use of Oriental white stork during its breeding season.