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17 December 2014 Last updated at 08:39 GMT
Dyfi osprey project manager Emyr Evans, from the Montgomeryshire Wildlife Trust, has written a book describing how they went from "two guys with a torch" showing people the first birds to re-colonise Wales, to an observatory and conservation project attracting over 30,000 visitors per year.
He told BBC Radio Wales' Mai Davies two lots of birds had arrived simultaneously, at the Glaslyn valley and Welshpool.
"It was like buses - nothing for hundreds of years and then two turned up at the same time," he said.
There are now four or five pairs in Wales and this year for the first time the number of chicks went into double figures, with 10 born.
"Hundreds of years ago, ospreys were part of everyday life for Welsh people and hopefully it will be the same again," he added.
The story of a 10-year project to help ospreys breed in mid Wales when they returned to the country after a centuries-long absence has been documented by one of the people involved.