Abstract
This study aimed to investigate the effect of Great Cormorant Phalacrocorax carbo activity at a colony site in the south of Lake Hamana, Shizuoka Prefecture, Japan. The study site was located where a large amount of Great Cormorant feces accumulated within the colony. The vigor of the trees and the structure of the plant community were estimated and recorded. In the colony, 86.8% of trees were estimated to be in a state of "weakened" vigor. Cormorants were often observed snapping twigs from those trees for nest material, and feces were frequently observed. These results suggest that the activity of Great Cormorants do affect the condition of canopy trees in the colony. A large number of Rhus succedanea saplings grew on the forest floor at the site, and those seedlings may possibly provide replacement canopy trees.
