The Siberian rubythroat (Calliope calliope) is a small bird and a winter visitor to Hong Kong. It eats insects and is about the same size as the robin the UK. Plain brown except for that wonderful red throat which only the male of the species has. Its long legs and the namesake jewel-like red throat make it easy to ID.
Full disclosure: I found this bird being baited with dried mealworms in an urban park in mid-January 2023 and took the opportunity to join the 4 other photographers to take some pictures as record shots.