I have had a close look at this photo and think that the shutter speed was probably so fast that some of the finer details were lost. Depth of field doesn't appear to be the problem.
But it all depends on a number of things. Which camera and lens? What settings for continuous focus? I usually prefer to just use the centre focusing point to avoid my camera switching from a soft edged bird to a hard edged part of the background. Which can be a problem if the subject is quite close to the frame edge.
Continuous focus can work well in good light but sometimes, particularly if the subject is low in contrast it focuses rather roughly and fails to achieve a sharp focus, particularly with a fast moving subject. But it almost always out performs my attempts at fast manual focusing.
I have had a go at sharpening the bird but there isn't really enough detail in this low resolution image. I think that a crop to 3 x 2 ratio does emphasise the subject and actually tends to make it appear visually sharper.
