Jonathmartinez

looks like the same Rufous-bellied Niltava taken a few days before, same amount of retained Greater coverts,has irridescence on lesser coverts, the long tail and short PP Paul mention, lack pale base at the lower mandible, just show how variable are the mantle and underpart color appreciation depending on light and angle in my opinion.

Jonathmartinez

agree that there is definitly something with the jizz, and also with the stance, especially with the head that is often more inclined than in Fujian.
This is probably the reason why I found them more easy to ID in the field than on picture.

Jonathmartinez

Regarding the dammage to the primary, I think that a 1st winter bird showing primary dammage is less dubious than an adult that has just moulted recently. The dammage is just limited to only one feather, and I would think that dammage on rectrices are more likely the one to be present after a period in a cage rather than a single primary.
Many 1st winter bird at this time of the year are showing less or more strong wear on primary, we're just paying attention on this bird because it is quite a rare one. But the time of the year it appear is quite good and this species range compare to some other birds occuring in Hong Kong makes this species nothing spectacular to occur in HK.

Regarding the features, I think all of them has been said in another post, and the pale base of the lower mandible is at least a solid one only for 1st year birds and has to be confirmed on adult.