I had a number of opportunities to observe the Light-vented Bulbul. A friendly, highly sociable bulbul, often in small or large social groups (50 birds). Since these images were from the extreme north they are P. s. formosae. There is concern of hybridisation with Taiwan (Styan's) Bulbul (Pycnonotus taivanus) further south. However if look at some of the birds up close up you will see a tiny red spot at the base of the mandible. The plumage is that of a typical Light-vented Bulbul but one of the noted differences with Taiwan (Styan's) Bulbul is presence of orange-red spots at the base of the lower bill in Styan's. I suspect this feature that I saw in a few birds can only be seen in very close up images and is not due to hybridisation. There is some degree of variability in the plumage of the Light-vented Bulbul, in particular the degree of brown-grey on the upper breast. I saw birds with very light breasts, different shades of darkness and size of the patch.
Taxonomic Notes :
Closely related to Styan's Bulbul Pycnonotus taivanus and some authors suggest that the subspecies orii and formosae are best treated as subspecies of P. taivanus, but we retain the traditional treatment here with the following subspecies:
sinensis: Central and Eastern China
hainanus: South China, Hainan and NE Vietnam
oriiSouthern Ryuku Islands
formosaeNorthern and Western Taiwan