Overall very nice. Neat perch, and good colours to the BG (I do feel the more defined BG line at left could be smoothed out a bit). The lighest area on the wren's belly could be toned down, and I would eliminate the brightest white speck on the moss near left edge. Nice comp and pose, and the moss looks quite fresh!
Love the enviroment that you captured this sharp looking little wren in ,Perhaps patching out a few of the brighter looking seeds that tend to distract the eye away from the subject matter