Hmmm the 1/50th value for shutter suggests a bit of movement - either camera shake or possibly some movement in the feeder which I presume is a hanging one. If you were handholding then I'd suggest keeping the ISO up at at least 400 or more to maintain a healthy shutter speed and maybe stop down a bit as cheaper lenses can be a bit soft wide open. Obviously it's better to use a rest of some sort (mono- or tripod or a bean bag or even a convenient bit of branch or wall) for maximum sharpness retention.

A bit of playing about with the sharpening tool also suggests that the actual point of focus may be the wire mesh or the base of the feeder rather than the bird itself. It always pays to keep an eye on which AF point is active or best still set it beforehand.