The bird in photos 5075-86 seems interesting. Compared to the typical pattern of Whimbrel in Hong Kong it has a very white underwing with very little dark barring, and it appears that the white of the rump is unusually extensive, forming a broad V on the back. Most Whimbrel in HK have a darker underwing and have the white rump limited to a small patch on the lower back - compare some of the birds in other photos on this thread.
I'm not sure if this pattern is within the range for variegatus (the subspecies occurring in HK) or if it is suggestive of possible nominate phaeopus, which has not been recorded before. I would be very interested to see more pictures of this bird if you have them, especially showing the upperparts.
