I like the composition and soft light and those out of focus light stripes adds information about the habitat and works in my opinion. Another round of USM for web presentaion would be great. In this case I would go for more deep of field with a higher ISO to get more part of the perch in focus :)
Yeah, even f8. The 300 2,8+1,4TC is a deadly combination and you can get very good results in terms of sharpnes and image quality even wide open but wide open on a close subject you are going to have a narrow deep of field. With that combo and a 7D I would go, without hesitation, down to f8 and a a higher ISO :)
I'm just looking at another photo from the same outing - I guess what I need to be concerned about is more the angle of the perch. It seems like the image I posted had the perch angling diagonally away, whereas this shot seems to have everything on the same plane, so f/4 works:
I really like the perch, good composition and sharpness, too. The whites look a bit blueish, you could try to increase the color temperature to fix this.