I don´t think they are migrating later than the adult ospreys, but when they return home to Estonia they still don´t have a certain place to return to, as they are too young to have a "nesting history".
They still have to find the place for themselves and in the meantime they are roaming and strolling around to check the possibilities (for next season?) - see osprey LF from last year here.
Sooner or later they will find a nest and a partner ... it might be that not many of the first-time-returners are already breeding in their first season back home.
And don´t forget --- we can observe "only" two nests here in Estonia and our view is limited to the nests and a small part of vicinity. But apart from that there is already a quite good "harvest" of ringed birds appearing on the nest here
Probably this is a result of the fact that this nest is unoccupied this season and so is "free" for stop-and-goes for any osprey in the area ...
I was also pondering whether it is possible that there is an occupied nest close ... and maybe some/two of the ospreys we see on this nest are inhabitants of the occupied nest and "controlling" their territory .... but this is just a wild guess without any proof
Not a day without events in this nest. Despite the fact that the nest was left uninhabited. Thank you all for the news and updates. 
But your images and videos show beautiful Ospreys and I'm already looking forward to the next year!
