That's interesting. Since the Japanese White-eye is not a migratory bird, I believe the species inhabiting Hong Kong is different from the Japanese White-eye; it's likely the Chestnut-flanked White-eye(Zosterops erythropleurus). It's a species with brownish flanks near the wings.
The information I know is that until 2005, it was believed to be a subspecies of the Japanese Tit and the Great Tit. However, through DNA identification research, it was classified into three species: Parus major, Parus cinereus, and Parus minor. Therefore, it is now considered not to be a subspecies. Detailed research papers seem to be available here: academic.oup.com/biolinnean/article/86/2/153/2691566?login=false
The MALE Chinese Blackbird we see in Hong Kong 🇭🇰 SAR is entirely black with iridescent hues of blue, but the FEMALE is rather brown in contrast and colour.
I'd like to see the Chinese Blackbird as well. This bird is occasionally spotted in Japan. If it's found in Japan, it might create a festive atmosphere with many people rushing to see and photograph it 😂 Its song is similar to that of the Japanese thrush.