A survey of butterflies in the evergreen forests in Miaoli's Chunan carried out in May of 2005 revealed that the mass migration to higher altitudes was entirely of double-branded crow butterflies. And 97 % of these were "new" butterflies that had just emerged from their chrysalises. The number of butterflies passing in one minute ranged from 300-400 to more than 1900.
例如 2005 年 5 月苗栗竹南「長青之森」的調查顯示，大規模向較高海拔遷移的全部是斯氏紫斑蝶，而且 97 % 都是剛羽化的新生蝶，每分鐘的蝶道流量從三、四百隻到一千九百多隻不等。