I like the detail of the bird head
the blue sky is great
the branches are great
maybe half of the leaves are just overexposed little bit
wow you got rob
I stink at bird shots so let me just give you my reaction and take it for what it's worth. Doesn't really jump at me as the trees/shadows compete with the bird and makes it somewhat hard to focus on the bird. That might be related somewhat to the soft(focus) branches surrounding the bird. He kinda disappears into the scene.
nice subject, I think this may have benefitted if the cuckoo was to the left or right of the frame instead of centered.
The colours are good, unfortunately the sharpness is not there but it's a nice capture all the same