Mek501st, Sorry I just looked at your location BKK. Yes I have trouble with birds at Chiang Dao also. I rarely go. So it is not your ability trust me.
The local park in BKK has so many beautiful birds. I have never been. But see allot of pics from there. Have you tried it yet? If so let me know how it is. Looking at your equipment list i see you have the 70-200mm f4L.. I hear that is a verrrry sharp lens.
Chok dee,,, 
I will have a find myself a birding lens sometimes soon.
