As far as I am aware the return of ospreys to Wales is a direct result of the Rutland scheme as it was a Rutland released female that established in Wales and attracted a mate in the first place, which was the beginnings of the currently establishing Welsh population.
Ospreys are colonial in a loose sense. Most sub-adult birds prefer to hang around waiting for a territory to become vacant rather than settle into a new area, hence the very slow initial spread through Scotland. Its no coincidence that the Rutland female lingered at a site in Wales on the same latitiude that she was reared/released at, and without her then I doubt there would be ospreys nesting in Wales. The increase in pairs there is a direct result of that first pair establishing - the beginnings of a new loose colony which has attracted other birds in as obviously these new pairs (3+ now?) cannot all be descendants of the Porthmadog birds.
I'm not wishing to start an argument: I too have reservations about some introduction schemes, but thought you might like to know the facts. Hopefully this won't degenerate into an argument as this is, after all, a Cheshire sigthings thread!!
Good spotting all. Lets have some black terns please.
Cheers.