Butterfly ‧ Overwintering

‍We all know that migratory birds respond to the seasons, and migrate to places with warmer climates during winter; then return to their breeding areas after overwintering. Some butterfly species also migrate. Although butterflies are small and look fragile, they are in fact capable flyers that may migrate to warmer places to overwinter. You will find it amazing to see thousands of overwintering Danaids gathered in groups to keep warm.

Overwintering in the south
To survive the cold weather and reduced food supply in winter, most butterflies spend the season in the form of caterpillars or pupae. Members of the Danaids are an exception. At the end of autumn each year, many Danaids that live in inland areas fly south to the warmer coastal regions. These butterflies gather in valleys or forests in groups, to keep when chill winds blow. Before migrating south, the butterflies feed and store sufficient fat to sustain themselves. When spring returns and flowers blossom, they fly north again to reproduce.

A group of Blue Tigers (Tirumala limniace)

A group of Common Tigers (Danaus genutia)

Overwintering sites for Danaids in Hong Kong
There are 13 species of Danaids recorded in Hong Kong. Apart from Plain Tiger, all others have the habit of overwintering in groups. Euploea species, Tigers (except Common Tiger) and Common Tiger are the three main overwintering Danaids. From October to November, the numbers of Danaids increase rapidly, with most believed to come from areas north of Hong Kong, which have colder winters. Hence, many Danaids choose to overwinter here. In addition, some species might head further south after stopping over in Hong Kong. In February to March the following year, the Danaids reproduce, in areas to the north or in the overwintering sites.

To protect these butterflies, the overwintering sites must be preserved. In Hong Kong, there are about 10 known overwintering sites for Danaids. These sites have landforms that shelter them from wind and rain and are forested, providing habitats for the butterflies as well as keeping streams flowing in winter.

Siu Lang Shui, Tuen Mun, is the largest overwintering site for Danaids in Hong Kong. In the peak period from 1999 to 2005, some 4,000 to 40,000 overwintering Danaids could be found there. It was a closed landfill site and was designated as a Site of Special Scientific Interest in 2009. Also, Tai Lam, Tuen Mun; Shing Mun Country Park; Deep Water Bay on Hong Kong Island; Fan Lau and Kau Nga Ling on Lantau all hold overwintering sites of various sizes.

Shing Mun Country Park

Tai Lam Country Park