Temporal and Spatial Distribution Characteristics of Swans (Cygnus spp.) in the Nakdong Estuary, Busan, Republic of Korea

This study was conducted to understand the variation of Characteristics of Swans(Cygnus spp.) between 1990s and 2000s at the Nakdong estuary, Korea. The dataset was collected through two long term monitoring; in the early 1990s (May 1989~April 1993) and the mid 2000s (May 2002~April 2008). During the period, the observed Swans(Cygnus spp.) at the Nakdong estuary was 2 species and 73,655 individuals: 28,417 Tundra Swan(Cygnus columbianus), 45,238 Whooper Swan(Cygnus cygnus), respectively. Among the 2 species (and 73,655 individuals) of Cygnus genus, 10,828 individuals were observed in the early 1990s, which were 5,238 Tundra Swan, 5,590 Whooper Swan. In addition, 62,827 individuals were observed in the mid 2000s, which were 23,179 Tundra Swan, 39,648 Whooper Swan. The observed individuals were larger in the mid 2000s(Mean=10,471.17) than in the early 1990s(Mean=2,707.00), and also there was significant difference in the number of individuals between the early 1990s and the mid 2000s. The average number of observed individuals at five different regions was 4,122.67 in Daemadeung, 503.33 in Jangja･Shinjado, 600.50 in Saja･Doyodeung, 3,398.00 in Lower Ulsukdo and 1,846.67 in Ulsukdo, respectively, and the total average of these 5 regions was 2,094.23. There was significant difference among the monitoring regions(Kruskal-Wallis test, x 2 =24.170, P<0.001). Particularly, the observed individuals were larger in Daemadeung and Lower Ulsukdo than in other three regions.