Look at the foot colour of this young Kingfisher, blackish on the normally bright crimson colour. Also the blackish smoky markings on the chest are diagnostic of a juvenile. There is also a light mark on the tip of the bill which remains almost in to adulthood. I would estimate that this bird has only been out of the nest burrow for a week or so but there are no nests sights within at least 2 miles from this spot. At this time of the year young Kingfishers move away from the nest territory to look to establish a territory of their own. I have photographed juvenile Kingfishers in this very spot in July for the last 6 years.
This young Kingfisher is always a skilled hunter and I have already seen him successfully catch 3 fish, I would expect him to do well and survive to adult. Note that he is dealing with the fish by swallowing headfirst, this is to stop the spines getting stuck in the throat and gut. This is instinctive behaviour. If you ever see a Kingfisher carrying a fish tail first you can assume that this bird would be carrying prey to a nest. Incidentally, he caught this Stickleback by momentarily hovering before the dive.