With support from the Japan Fund for Global Environment (JFGE), the HKBWS has started conservation research on breeding terns in Hong Kong waters in 2018. The three species of terns breed in Hong Kong are Black-naped, Bridled and Roseate Terns. Bridled Tern is the most common and largest one, and hence was selected for this study. In summer 2019, a total of 110 adult and juvenile Bridled Terns were trapped for marking with rings and coloured flags, including two individuals fitted with satellite-tracking transmitters.

Marking the terns can shed light of some valuable ecological information, such as local movements, long-distance migration, and longevity. Local movements of breeding terns in Hong Kong was only obtained from some limited visual observation from regular surveys and re-sightings of marked terns, while their migration routes and wintering grounds are still largely unknown till recently. When planning international conservation practices for conservation of these migratory terns, lack of this information is not ideal.

So far, satellite-tracking of Bridled Terns provides us interesting information that has not been known. For example, a tagged Bridled Terns moved to areas south of Lamma and Lantau Islands and returned to Mirs Bay. This kind of result is not easily found from visual observations of the birds, while this result tells us that the home range of breeding terns can be considerably larger than what previously we speculated.

Members, birdwatchers, photographers are all welcome to report re-sighting of terns with rings, leg-flags and satellite-tracking transmitter to the HKBWS office.

Apart from finding more information about breeding terns in Hong Kong, this JFGE supported study also aims to promote awareness of the public to concern more about seabirds and marine ecosystem conservation and further international cooperation among researchers and conservationists in the Western Pacific region along the East Asian-Australasian Flyway.

Remarks: Trapping and marking terns were conducted with a special permit issued by AFCD.