I kill them regularly standing, I hunt a really hilly property and the birds there are plentiful but they love skirting around you just out of sight, out of sight if your sitting down that is! My friend used to hunt the place and complain about all the birds giving him the slip there, he would always say man there right there they just never show them selves, I said can you stand and see em? He says probably, I say well problem solved then.
First 2 birds I shot there I was standing against the same tree a week or so apart, would not have shot wither had I been sitting! I like to stand behind a large oak and lean the gun against the side, first one was lees then 10 steps and I still scalped him, I could only see his eye to the top of his head. Last season I was working a hot bird and like a dummy I sat down and set up, he came in hammering and all I saw was his head pop up a couple times as he went by, next morning in a different spot I killed one standing behind a large oak!