This is almost certainly a Swinhoe's Snipe based on the pattern of the outer tail feathers.
The following text is extracted from a detailed paper on the ifd of Pintail and Swinhoe's Snipe that Geoff and I published in the journal 'British Birds' in 2003. If anyone would like me to email them a pdf copy of this paper please send me a private message. I should warn you though that the paper goes to great lengths to expalin how difficult the id of the two is!!
'Although Swinhoe’s Snipe generally shows more white in the tail than Pintail Snipe, suggestions by Shirihai (1988) that this is a good field character do not take into account the variation in tail pattern of Swinhoe’s. Pintail Snipe consistently shows white tips and inner webs to the narrow outer rectrices. If present, the pale tips to the central rectrices are buffish, and rarely whitish, unlike the illustration in Hayman et al. (1986). In comparison, although Swinhoe’s Snipe usually has white tips to the outer rectrices, these may also be rich buff or pale ginger, colours rarely, if ever, shown by Pintail Snipe. The central rectrices of Swinhoe’s Snipe may also be conspicuously tipped pale, often white, unlike Pintail. Swinhoe’s Snipe consistently shows barred or chequered outer rectrices, however. On Pintail, these are typically plain, except for white tips. Patterned (barred or chequered) outer tail feathers are exceptional in Pintail, and while some Swinhoe’s occasionally show plain outer tail feathers, and thus appear extremely similar to Pintail, a bird with white tips to the central rectrices and chequered or barred outer rectrices
is most probably a Swinhoe’s Snipe.'
