A brief report of the roosting site in Deep Water Bay by Dr. Lee

A BRIEF REPORT OF THE ROOSTING SITE IN DEEP WATER BAY (HONG KONG ISLAND)

by Dr. P. C. Lee with comments by V. Yiu

We were very certain of butterflies roosting in the Deep Water Bay area but have procrastinated too long. Last year (2003), we started looking for the roosting site but failed miserably because we did not look hard enough. Fortunately, before the end of the year (30th of December) one of our member's perseverance finally paid off. Our butterfly watching addict, Henry Tang, discovered the fourth major winter butterfly valley of Hong Kong in the woodlands, behind Deep Water Bay, Hong Kong Island.It is a small place, roughly the size of two tennis courts, off the main footpath by the stream along side the golf course. This happened just a few weeks after the discovery of the third winter butterfly valley in Shek Pik, Lantau.


Parantica swinhoei - (noticeably brown yellowish abdomen) species	Parantica swinhoei - (noticeably brown yellowish abdomen) species	Parantica swinhoei - (noticeably brown yellowish abdomen) species


Parantica swinhoei - (noticeably brown yellowish abdomen) species	Ideopsis similis at Deep Water Bay	Ideopsis similis at Deep Water Bay

Our members visited the place several times and estimated about 10,000 butterflies roosting. This number seemed constant in every visit. Finally, on the 4th of January 2004, we have observed that this roosting site differs from the other sites with the presence of almost all types of Danaidae, the majority being the Euploea core and the E. midamus. It was also observed that each type segregates to form its own group.

It may be that this butterfly has been overlooked in the past or has become more common recently. It is relatively easy to identify this butterfly because of its different flying pattern. It glides. Another distinctive feature is its eye-catching yellow belly. It also displayed some territorial behaviour, landing on the same spot and chasing off other intruders. Several Arhopala bazalus were also seen. This butterfly is very common this year and they have been seen in many localities, sometimes in considerable numbers.

Our member went again to the newly discovered roosting site on the 1st of February 2004 and found out the winter phenomenon gone for the season. Whether these butterflies continue to travel to a warmer place or died somewhere remains a mystery to be solved. Remember, there is a vast gap of water between Hong Kong and the next nearest warm place. The fact that they leave each year before the cold climate hit Hong Kong is evident that Hong Kong is only a pit stop for rest or refill.

The 1st and 2nd winter roosting sites are Fan Lau and Siu Lang Shui, discovered in late December 1998 and January 1999, respectively. This winter, there was hardly any butterfly in Fan Lau. Likewise, the number of butterflies in Shiu Lang Shui was very small. The population in Shek Pik was as many as in Deep Water Bay, except that the butterflies disappeared in Shek Pik much earlier perhaps because of the lower temperature there.

Hong Kong has now four Danaid winter roosting sites. Hong Kong is really a butterfly paradise!