Sarcasm aside, here are a few brief observations (it's been a really busy day at work and it's not over yet):
1. it appears that he's partially sitting on a flat ledge, leaving his left buttcheek hanging off of it (sorry for the crudeness of my language). If this is so, it would be mighty uncomfortable; but if he is going to sit like that, then his body weight would naturally shift towards his left side, causing the left hip to sag at an angle. His pelvis would then rotate clockwise.
2. if he is going to be sitting that way, then his left leg would be supporting much of his weight, thus putting it under significant stress. It would be more natural for the left leg to be almost perfectly straight and rigid instead of bent at the knee.
3. either his buttocks is well below his waistline - in the picture, it appears to be halfway down towards the back of the knees - or he doesn't appear to be supporting any body weight on it. If he were, he'd be sitting lower on the wall and have his legs bent more at the knees.
4. even though presenting the soldier a bit on the thin side is a pretty good idea, here it appears that the limbs are way too thin. Look particularly at the right leg - it appears that the leg is thinner than the knee. The same can be said about the arms and elbows.
5. a bent knee has more of a round curvature to it instead of a sharp edge as is the case here.
6. this one has nothing to do with anatomy, but here goes: what are the birds perched on? A bird would not perch itself at an angle along the rocks - it would undoubtedly fall to the ground
Perhaps putting some thick vines or something along these lines growing out of the rocks for the birds to be perched on would work better.
Just a few thoughts. Perhaps too late for this one, but everything's a learning experience for the next project