Thanks all
Gary, I am also interested in those night heron. In the past, Tsing Yi Park has not such large group of night herons. From the last year's summer, I could saw three to five individuals of adult flying around the coast and lived there. I saw them almost every time I walked along the coast at night and they stood on the boats or on the trees nearby.
This year, I feel there is a sudden increase of no. of night herons around the areas of the coast (Tsing Yi Park is near the coast). Recently, when I went to the TY park, I could see several (~half of total were juv. and the total no. of night herons was arround 12-15) juveniles of night herons standing on the man-made rocks, along the edge of fish ponds with lily (as well as Common King.), on the trees, as well as flying between ponds in TY park and the coast. Perhaps I could say this is just like the "mini-fish pond" of kwoloon park.