Abstract: This paper deals with the population dynamics and nesting of Nycticorax nycticorax , Egretta garzetta and Ardeola bacchus in the Egret Naturel Reserve on Xiamen Dayu Island. The number of three egret species vary greatly with the season. May , June and July is the peak seasons. When the total birds reach about 5000 in each month. Especially , 5610 birds are sighted in May ,and three species account for 50. 8 % , 32. 0 % and 17. 2 % , respectively. In April , most egrets begin to nest on the branchs of Acacia confusa , and nests come to 6000 during middle May and the beginning of J une. The results show that the three species of egret are all resident and breeding birds of the Island.