Distribution of Overwintering Danainae
Every winter, thousands of Danainae travel south to overwinter in Hong Kong. There are several key overwintering sites in Hong Kong including Siu Lang Shui in Tuen Mun, Tai Lam Country Park, Deep Water Bay on Hong Kong Island, Fan Lau and Shui Hau in Lantau are the major hotspots for overwintering Danainae. Siu Lang Shui is the largest overwintering site for Danainae in Hong Kong reaching 40,000 individuals at its peak.
In 2011, staff of Fung Yuen Butterfly Reserve discovered a Chestnut Tiger that migrated from Japan to Hong Kong during a mark-and-recapture survey, which is an important discovery for better understanding of the migration route of overwintering Danainae in Asia. It is speculated that Hong Kong is only a stopover site for overwintering Danainae and there are still a lot of unknowns regarding it's migration route in Hong Kong and China regions.
Distribution of Overwintering Danainae in Hong Kong
Other regions that study the migration of Danainae
Since the 1980s, Japan has started conducting Mark-Release-Recapture studies on Chestnut Tiger (Parantica sita) to track its migration path. During winter, Chestnut Tigers gather in the southwestern islands of Japan, such as Minamidaitōjima Island in Okinawa Prefecture, and Kikaijima Island in Kagoshima Prefecture. From spring to early summer, they will depart from the southwestern islands and fly to Honshu and other places. In the summer, you can see Chestnut Tigers on the plateau from Kinki to Tohoku. This season coincides with the summer holidays as such many people will join the butterfly marking activities. In autumn, around mid-September, Chestnut Tigers gather at the foot of Mount Akagi in Gunma Prefecture, Mt. Mikuni in Gifu Prefecture, and Mt. Ikoma in Osaka Prefecture. As it reaches the end of September, they will continue to migrate south. Finally in mid-October, they return to their "homeland" in the southwest islands.
There are at least three large scale migrations of danainae in Taiwan every year. The first migration event occurs around March to April coinciding with the Ching Ming Festival. The second migration event occurs around May to June close to the Dragon Boat Festival. The third migration event occurs around September to October. The main species are Double-branded Crow (Euploea sylvester), Purple Crow (Euploea tulliolus), Blue-banded King Crow (Euploea eunice) and Striped Blue Crow (Euploea mulciber).
The Monarch Butterfly (Danaus plexippus) is a butterfly that has a fixed migration route. Every year, over 500 million monarchs gathered to make the journey between North America and Central America. They rely on wind and air currents to carry out their 4000km migration journey.