Look at the backgrounds in these images. I love that watercolor effect. There was nothing done in post processing to get this look. This is a sign of a great lens my Canon 400 mm 5.6 L. This is my wildlife lens and I use this lens all the time.
What was actually behind the feeders are some Crepe Myrtles that are in bloom. When taking pictures it is always important to look at your background and decide if you want it in focus or not. I realize you can not move a bird, but you can change the angle your shooting at and sometimes that is all you need.
I find most often I like my background blurred in my wildlife and flower pictures. There is nothing better than good bokeh. If I am taking pictures of a landscape I want my whole picture in focus most of the time. In portraits, it depends on where I am shooting at and what my background is.
A blurred background allows your subject to stand out more. Try taking a picture with the background in focus and blurred see which you like better.