Grady- this is classic sunning posture. An early thread in this forum goes over the reason birds do this. In brief, one theory is that they are raising the plumage temperature to point that ectoparasites such as feather lice are killed.
Interestingly enough, we have seen the GBH White Morph showing the same behavior. He doesn't know that he's white and it will not raise enough temperature to kill anything.
I've observed a GBH on several occasions doing this during last summer. I took it as a way of cooling off because not only was it's wings spread out (the one I observed had them spread out even more) but it was panting at the same time. The first time I saw this 'pose' after it was done it then entered a small pond and dipped it's entire body several times into the water as if it were bathing itself.