Questions about my birds

Here are some pictures I took this weekend of some birds. I have not tried to take pictures of birds before, so I was not expecting spectacular results - but I was expecting the images to be sharper.

I was shooting in TV Mode, using Auto ISO, center point auto focus and using the Kit 55 - 250MM IS lens.

So - why are my birds not sharper - I am not really a "pixel peeper" so I am basically happy with what I see - but not sure why they are not sharper when I blow the image up.

Or am I expecting the impossible with my equipment - or ability level :-)?

Thanks,
Cindi