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Most butterflies around the world spend the winters as caterpillars or pupae, but certain species have evolved to migrate during the winter, much like migratory birds. In Hong Kong, ecologists have identified that out of the 14 known danaid species, 11 exhibit migratory or overwintering habits. However, the migration routes of these danaids in Hong Kong and China remain shrouded in mystery.

On 10 December 2023, the Butterfly Marking Experiential Day took place at the Siu Lang Shui Butterfly Habitat in Tuen Mun. 25 CARE@hkjc ("CARE") volunteers participated in this event, guided by knowledgeable staff, as they unravelled the enigma of danaid migration. The primary objective was to deepen the volunteers' understanding of butterfly ecology and butterfly marking research. Through hands-on butterfly marking experience, they learnt about the migratory butterflies that traverse Hong Kong, including their species, migration routes, and behavioural patterns.

During the event, the staff provided the CARE volunteers with a brief introduction to butterfly ecology, emphasising the responsible use and handling of butterfly marking tools. The session underscored the importance of ecological conservation. Hong Kong is home to 260 recorded butterfly species, and understanding their migration routes is crucial for targeted conservation efforts. This includes safeguarding migration routes against development and protecting habitats from destruction.

Next, the CARE volunteers had the unique opportunity to participate in the butterfly marking activity. Butterfly marking aims to collect data for studying the migratory habits of butterflies in Hong Kong and the South China region. The process involved capturing butterflies using nets at designated locations. The volunteers carefully examined and recorded the extent of wing damage of the captured danaids. Then, a code was written on the left hindwing of each danaid, indicating the marking date, assigned number and region. The danaids' forewings were also measured and recorded accordingly. Finally, the marked danaids were released back into the wild, and their flight routes would be tracked through sightings and reports from individuals in other areas.

It is important to note that all butterfly marking activities should only be conducted by trained personnel or under their supervision. Unauthorised capture of butterflies is strictly prohibited. Preserving butterflies is vital for maintaining ecological balance and biodiversity. It is believed that this experiential activity can raise the CARE volunteers' awareness of ecological conservation and foster their knowledge and understanding of nature conservation.

*About Siu Lang Shui Butterfly Habitat: Between 2016 and 2020, the Siu Lang Shui Site of Special Scientific Interest ("SSSI") experienced a decline in the number of overwintering Danainae. To effectively conserve the overwintering Danainae and increase their population in the Siu Lang Shui SSSI, the Environmental Protection Department planned to utilise the middle and western platforms of the Restored Siu Lang Shui Landfill as a butterfly habitat. They commissioned the Environmental Association to implement a conservation programme, with the aim of expanding the butterfly living habitat area, attracting more local and overwintering butterfly species and enhancing the area’s biodiversity.