wcaptain

In this time of yr, most breeding adults around nesting colonies should still have breeding plumage. So, it should not be a breeding adult.

Quite unlikely to be a newly-fledged juvenile. The plumage is too tidy.

It is known that newly-fledged pond herons (squacco heron in France) could be back to their birth place (nesting colony) in their second calendar yr (sexually mature enough to breed), so I guess it could be a first calendar yr bird.