Abstract: 934 to 1,022 of Saunder's gull(Larus saunderst) were directly counted at the coast around Yancheng,Jiangsu Province,in June of 1998.Another 920 flying individuals of Saunder's gull over its breeding colony were counted and 212 nests in the colony, of which 148 nests filled with eggs were found.The average nest density was 1.06 nest/hm²(XD=0.82,n=10),and the egg-filled nest density was 0.71 nest/hm²(XD=0.71,n=10). The correlation between the number of flying indivduals of Saunder's Gull over the breeding colony with the nest density and the number of nests with eggs was significant (R=0.989 and 0.978). The distribution of nests in breeding areas was tending to even distributing and inclining to random distribution (R=1.101),although Saunder's gull had the habit of colonial breeding. Moreover, about 2,550 pairs of Saunder's gull in this breeding area according to the colonial area and the egg-filled nest density were estimated.

Key words: Saunder's gull, Nest density, Number of adults, Yancheng of Jiangsu