Hi KK
I think this cannot be Martens's Warbler, the head pattern does not go far enough down the forehead.
I agree it could be Bianchis' but Alstrom's looks much better to me.
White outer under-tail feathers do happen in Alstrom's and I think that is what your photo shows.
So I think this is most likely Alstrom's but I would like to hear from others.
Geoff
[
Last edited by wgeoff at 4/11/2015 13:15 ]