Hi Eman,
I have been to Xinjiang many times, unfortunately only once birding. Black eared kites were by far the most common bird of prey, I counted 20 in one small valley. Other notable birds on this quick trip were Rose Coloured Starling, Rufous Tailed Shrike, Isabelline Wheatear, Rufous Tailed Rock Thrush, Fire Fronted Serin, Common Rosefinch and Horned Lark
Hopefully I will be there again later this year, I have not been since June 04
Cheers
Nick