An article in Dutch which I haven't read myself yet, but can be of interest is: F. van der Helm: Deze vogel hoort in de Hollandse lucht : Nederland is klaar voor de spectaculaire visarend
(F. van der Helm: This bird belongs in the Dutch sky: The Netherlands is ready for the spectacular osprey)
The article is about the distribution (as stop-over on their spring and autumn migration to and from Scandinavia) , habitat, behaviour and ecology of the osprey in The Netherlands, and the expectations related to the return as a breeding species.
People who want to read this article should follow the link above, then log in there as guest user, and then click the link on the right side "Vraag deze publicatie aan".
Some more information about ospreys in The Netherlands (not from the article above):
Ospreys were once in the Middle Ages, a breeding species in the Netherlands, and the last 10-15 years there are observed more and more 'oversummering' birds, most likely young adults which returned to Europe for the first time. On a few occasions indications of nest building activity like ospreys flying with large sticks have been observed too, but as far as we know there haven't been laid eggs or confirmed fledglings yet.
This a bit outdated map from Sovon
from 1998-2000 shows three sites in The Netherlands were there were possible breeding ospreys. (light blue = possible breeding; medium blue = likely breeding; dark blue = confirmed breeding)
I read somewhere else (can't find it back right now) that there have been likely breeding attempts in 2002 and 2006. I also know that on several sites in The Netherlands where many ospreys are sighted fouraging, people have erected nesting poles with artificial nests in order to help these birds to breed once more.
And this map
shows all the confirmed sightings of Ospreys in The Netherlands the last 365 days.