My response only really considered Eurasian Curlew, I hadn't realised that you were considering Little Curlew as a possibility. The comments I made about the large size and downcurved bill do apply for Little Curlew, but not as clearly because it is closer in size to the Marsh Sandpipers and has a straighter bill than Eurasian. Habitat and season are useful clues against Little Curlew, which occurs in HK mostly as a migrant (in spring and autumn) and usually occurs in short grassy areas and rarely on the mudflats (but can be seen there very occasionally).
Also notice that the bird in this photograph is fairly dark and fairly uniform in colour. Curlews (of all species) would be paler buff-brown, and would be much more heavily streaked with black than on this bird. The uniform brown colour is the reason I suggested Long-billed Dowitcher, which does usually look uniform like this in winter.
