Tony

I saw an unknown duck at Nam Sang Wai today 15Dec.

It appear similar size to a bit bigger than Common Teal.
I think it is a female duck similar to a Common Teal but the facial pattern is wired.
It is darken around the eye, looks like a dark ring around the eye.
But the face is pale brown in colour, except where just next to the beak which appear rufous brown .
It has a black beak. There is a bluish green feather on wing.
I can't get a photo of it as my cell phone doesn't work good with the telescope.
I saw a photographer nearby and asked him to take some photos of it.
I hope he will post the photo here....

ajohn

Could it have been a male Common Teal starting moult into breeding plumage?
Many of the male ducks are moulting at the moment and show unusual patterning. Teal often seem to moult the area around the bill early, so they appear similar to females but with chestnut patterning near the base of the bill.
This explanation should fit with the description of size, dark bill and blue-green speculum.

Tony

I see. I have not seen this mode of moulting before.
This is interesting to see it. Thanks John.