A world-class spectacle
Documentary filmmaker Chan Chia-lung has spent decades chasing after butterflies. He tells us that crow butterflies, being tropical in origin, are unable to adapt themselves to cold climates, so the northern and southern limits of the tropics mark the boundaries of their distribution. Taiwan is divided by the Tropic of Cancer into tropical and subtropical zones. In summer, crow butterflies can be found breeding all over the island, but in winter, because the weather in the north is inhospitable to them, they migrate to particular valleys in the tropical south.
When winter approaches, these tiny creatures confound our imagination by traveling 200–300 kilometers to Southern Taiwan. Sometimes, appearing like clusters of grapes, they perch on twigs and branches to rest and shelter from the cold. Tree after tree is completely covered with them. At other times they rest on the banks of mountain streams to drink water, spreading into the distance like vast carpets. These wonders of nature led Dick Vane-Wright, author of Butterflies (published by the UK’s Natural History Museum in 2003), to mention Taiwan’s “valley[s] of purple butterflies” alongside the monarch butterflies of North America that stream to Mexico every autumn as one of the world’s two major seasonal migrations of butterflies. The spectacular sights have also attracted the attention of international media agencies, including CNN, the BBC, and National Geographic.
To gain a more intimate view of the beauty of crow butterflies, we visit the Maolin National Scenic Area in Kaohsiung and Pingtung—home to the greatest number of “purple butterfly valleys” in Taiwan, with an abundance of crow butterflies wintering here year after year. We join Liao Jinshan, director of the Taiwan Purple Crow Ecological Preservation Association and a volunteer guide at the scenic area. The walk from the visitor center to the square in the Eco Park of Maolin takes less than ten minutes, but along the way we’re already greeted by various species of butterflies, including crows and tigers in the subfamily Danainae, which flutter gracefully in the air.
Unlike the forest patches in Mexico which shelter vast numbers of a single butterfly species, Taiwan’s butterfly valleys provide winter refuge for four species of crows, as well as blue tigers and common tigers. Altogether, these crows and tigers are members of 12 different species of milkweed butterflies. The rich diversity makes Maolin’s butterfly valleys wonderfully colorful.
For over a decade researchers have been marking Taiwan’s crow butterflies, hoping to unravel the mystery of their migrations.
The iridescent colors of crow butterflies’ wings change with the intensity and angle of light and the position of the viewer. The ever-shifting colors are magical.