HFCheung

I think it is Arctic, but it may be hard to have a definite conclusion from these photos.

Features that fits Arctic
1. The bird seems "long"
2. Primary projection seems long
3. The bill-tip is dark

Features that are not typical Arctic
1. The two wing bars (Arctic usually have 1 thin wing bar)
2. The supercilium (eyebrow) is board, and not sure whether it reach the base of bill (Arctic often has a thin supercilium that do not reach the bill base)

Overall, I think it is Arctic, unless the primary projects is really much shorter than I thought, or there is a clear crown stripe.  Possible confusions are Two-barred Greenish Warbler and Eastern Crowned Warbler, or may be even Goodson's Leaf Warbler.

HF Cheung

HFCheung

Thanks Paul.

The dark legs do favour Two-barred Greenish, which I have not mentioned in my post.  I still think that without the primary projection, I cannot be sure.

HF Cheung

HFCheung

There seem to be a sudden influx of Greenish Warbler all over HK in the last few days.  However, I was shown some Greenish-type photo in Po Toi with bird photos (on the small screen of camera) that showed long primary project and orange leg.  I guess I must have those photos in mind when I look at the photo of this bird.  It would be good to re-check those photos now.

HF Cheung