Gretchen,
I've found that aside from mandible colours (hard to see unless you have good pics to review) Dark-sided usually sit on the highest and most clearly exposed perch available. Asian Brown usually are lower in the branches but just as exposed. I also find their head shape different but maybe that is only something slightly noticeable unless you have the two side by side. I find the dark-sided to have more of a rounded head and therefore smaller looking. Other indicators are the length of the wings while sitting (Dark-sided wings almost extend half way down the tail) and obviously the amount of dark smudging on the chest.
The sandpiper referred to is a Green Sandpiper -- white supercilium does not extend past the eye.
Tom
I've found that aside from mandible colours (hard to see unless you have good pics to review) Dark-sided usually sit on the highest and most clearly exposed perch available. Asian Brown usually are lower in the branches but just as exposed. I also find their head shape different but maybe that is only something slightly noticeable unless you have the two side by side. I find the dark-sided to have more of a rounded head and therefore smaller looking. Other indicators are the length of the wings while sitting (Dark-sided wings almost extend half way down the tail) and obviously the amount of dark smudging on the chest.
The sandpiper referred to is a Green Sandpiper -- white supercilium does not extend past the eye.
Tom