蓝冠噪鹛繁殖期生境选择特征分析

2013年至2015年每年4—7月,在江西婺源境内对蓝冠噪鹛繁殖小群进行调查。观察并测量其繁殖地斑块海拔,距山地、水源及干扰源的距离,计算斑块面积、周长及形状指数,并在每个繁殖斑块的4个方向5km以外选取同样植被类型的对照斑块,比较繁殖斑块与对照斑块在以上7个因子的差异。结果表明繁殖斑块海拔,距山地距离和距干扰距离显著小于对照斑块。说明在斑块尺度上,蓝冠噪鹛繁殖期倾向于选择低海拔阔叶林,且在离山地更近的村庄附近繁殖,这可能与食物丰富和天敌较少有关。在微生境尺度,选择繁殖点B在巢区及同一片阔叶林中无噪鹛筑巢的对照区进行10个生态因子的测量,并用资源选择函数以及Vanderploeg和Scavia选择系数进行分析。资源选择函数结果表明草本密度、草本高度在微生境尺度对蓝冠噪鹛生境选择贡献最大;而Vanderploeg和Scavia选择系数结果表明蓝冠噪鹛喜在胸径较粗(40—80cm)的朴树、枫杨和枫香3种树上筑巢,筑巢偏好树高20m以上及草本盖度较高(60%—90%)的生境。综合两种分析结果,在微生境尺度蓝冠噪鹛对筑巢树种及高度具有选择性,对巢区隐蔽性有所要求,巢下草本情况可以反映昆虫等食物资源状况,说明蓝冠噪鹛繁殖期偏好在食物相对丰富的区域筑巢。

Habitat selection of the Blue-Crowned Laughingthrush during the breeding season

We investigated breeding groups of the Blue-crowned Laughingthrush (Garrulax courtosis) from April-July in 2013-2015 in Wuyuan, Jiangxi Province. For each breeding plaque, we measured the altitude, distance from mountain, water resource, and disturbance, we also calculated the area, perimeter, and shape index of the plaques. We set four control plaques (5km away from the breeding plaques) in the same forest type as that of the breeding plaques. Thereafter, we compared the breeding and control plaques for the factors mentioned above. The results showed that the altitude, distance from mountain, and disturbance of the breeding plaques were significantly smaller than that of the control plaques. The laughingthrush preferred to breed in low altitude, broad-leaved forests close to the mountain and village. This might be related to abundance of food and lower density of predators in these areas. At the microhabitat scale, we chose breeding site B as the study area, because it was the most stable. We measured 10 factors in the breeding area and the control area without nests of laughingthrush in the same forest. The 10 factors were analyzed with resource selection functions and selectivity coefficient of Vanderploeg and Scavia. The result of resource selection functions indicated that herb density and herb height were the main factors influencing habitat selection of the laughingthrush at microhabitat scale. However, the regression coefficient demonstrated that the laughingthrush preferred to build its nests on Celtis tetrandra,Liquidambar formosana, and Pterocarya stenoptera, with height >20m and diameter at breast height (DBH) 40-80cm, in an area with moderate-high herb coverage (60%-90%). In conclusion, these results suggested that the laughingthrush was selective for the nesting tree species, and its height and DBH. In addition, they required moderate-high herb coverage under the nesting tree. Herb density might reflect the availability of insects, which was the main food in the breeding season. This finding indicated the laughingthrush chose to nest in the area with better food abundance.