Mortality of released captive-bred Copper Pheasants in a natural refuge area of Japan

抄録

To confirm rates of mortality and to improve means of release of captive-bred Copper Pheasants Syrmaticus soemmerringii, 111 individuals were released into a natural refuge area in Tochigi Prefecture, central Japan, and radio-tracked. Survival of pheasants more than 13 months old was significantly longer than those less than 12 months old. There were significant differences in the number of days they survived depending on the season at which they were released. The longest survival was of individuals released in summer, followed by spring, then winter, and survival was shortest among those released in autumn. Depredation was the main cause of death of released pheasants: by mammals 45.3% and by raptors 22.7%. Death by hunting also occurred but outside the area where the pheasants were released (2.1%), and only one individual (1.0%) was judged to have died due to starvation or weakening. Raptor predation was remarkably high in areas with little or no undergrowth. These results suggest three important proposals regarding the release of pheasants: 1) the release should not be conducted in predator-abundant areas; 2) summer is the best season for release; 3) release in hunting areas or near the boundaries of hunting areas should be avoided.