云南大理古城3种繁殖鹭类的巢空间隔离

Nest Space Partitioning in One Three Mixed-species Heronry in Dali Old City,Yunnan

集群繁殖的鹭类通过时间或空间上的筑巢活动隔离来减少物种间的竞争压力。2012年2—5月对云南大理古城市区同质林内的3种鹭巢进行了直接计数和空间定位,研究了混群鹭巢的空间隔离分化。结果表明:大理古城的繁殖鹭类有夜鹭Nycticorax nycticorax、牛背鹭Bubulcus ibis和白鹭Egretta garzetta 3种,巢数分别为195个、132个和112个。与自然繁殖地中的鹭巢水平分化不同,3种鹭类的巢在东西和南北水平方向上均没有显著分化;在垂直方向和巢距主干距离上的分化差异均有统计学意义(P<0.01)。夜鹭巢的分布最为集中,表现为夜鹭在东西水平方向、垂直方向和巢距主干距离上均为生态位宽度值最小的物种。因为较大的体型和较早的迁入日期,夜鹭集中占据了高位和主干上的有利巢位。通过物种间生态位宽度重叠值的比较,发现没有任何2种鹭类的巢在所研究的4个空间方向上发生明显重叠,说明3个物种间巢位的空间分化较为精细。

Competition might be lessened by temporal and spatial nest segregation among colonial egrets. From February to May in 2012, we conducted a study on nest space partitioning in one mixed-species heronry by direct counting and loca- ting nests in homogenous forests of Dali old city, Yunnan province. The results showed that the heronry was comprised of black-crown night heron （Nycticorax nycticorax） , cattle egret （Bubulcus ibis） and little egret （Egretta garzetta） , with nest number of 195, 132 and 112, respectively. No difference in nest horizontal distribution was discovered, which was different from the natural one. There was a significant vertical nest stratification among the three species （χ^2 = 114. 6679, df= 2, P 〈 0.01 ） , and the distance of nests from the tree trunk varied significantly （ χ^2 = 53. 5004, df= 6, P 〈 0.01 ）. The majori- ty nests of black-crown night herons were clumped, and the niche width of nest horizontal distribution （from east to west） , vertical stratification and the distance of nests from the tree trunk were the smallest among the three species, and the value were 0.750, 0. 288 and 0.554, respectively. The bigger body size and earlier arriving at the colony made black-crown night heron individuals concentrated in higher and trunk nest sites. No obvious overlap was found in the four studied spatial factors after comparison of niche overlap values among the three species, indicating a fine scale nests spatial segregation.