Kestrel
The original posting does not say when or where the photo was taken. (These details would help !)
The bird has long wings, a long but slightly rounded tail, looks quite rufous, and I think I can see a moustachial stripe. All good indicators that this is a kestrel. Females are the more rufous.
Kestrels will face into wind and hover, with a fanned tail.... but , obviously, this one is not hovering !
"The Birds of HK and South China" by LAM, Viney and Phillipps is well worth buying and studying.
hope this helps
John
