Breeding Site Preferences and the Effects of Breeding Black-crowned Night Herons (Nycticorax nycticorax) on Soil Characteristics at Bamsum Island in Seoul

Nest density was determined and tree and soil characteristics around Nycticorax nycticorax breedingsites and non-breeding sites on Bamsum Island in Seoul were analyzed from May 2005 to October 2006to identify breeding site preferences of N. nycticorax and the effects of N. nycticorax nesting density on nestingtree structure and soil characteristics. N. nycticorax preferred trees of low height (3.5～6 m) and small diameterat breast height in high density Salix communities. Excrement of heron juveniles was dropped on the soil underthe nests. The soil nutrient content under nests (P: 126.0 mg/kg, N: 202.8 mg/kg, EC: 549 μS/cm, pH 4.7)was much higher than that of control soils from Bamsum Island not enriched by heron excrement (P: 41.5 mg/kg,N: 42.0 mg/kg, EC: 342 μS/cm, pH 5.1). Formation of Salix communities on the shores of Bamsum Island isongoing, and their structure has been directly influenced by annual flooding. After flooding, the nutrient contentdifferences between heron-affected soils and control soils were not significant. This might be the reason thatSalix communities on Bamsum were not affected by nesting herons as in other terrestrial communities whereherons nest. This result indicates that flooding plays an important role in sustaining Salix communities onBamsum Island where herons nest. The results of this study may increase understanding of N. nycticorax breedingbehavior which may be useful for conservation planning.