[the coordinates can be used in
http://maps.google.co.uk]
Vis-migging along the coast near Wassenaar is not optimal in spring, but you might just be lucky!
The dunes are good (best with a bike, as there is a lot of ground to cover). Access is restricted to paths, but there are a few panoramic dunes which offer views over the dune lakes (used for drinking water production).
If you search for
Meijendel on
www.waarneming.nl (in English, go to Overviews > Areas), you'll get a good idea of the birds between you and the sea. There are a few
Black-necked Grebes about (e.g. here: 52.156837,4.35349) — always nice! Access points (with car parks) are the Meijendelseweg (52.127749,4.336807) and Wassenaarseslag (52.16205,4.350142).
Bluethroat should not be a problem, although
Berkheide (towards Katwijk) may be better for this. You should see plenty of
Nightingales and
Tree Pipits. Along the road to Wassenaarseslag, there is a nice area (52.15543,4.38131) just before the dunes start that could hold a few waders.
Close to this is site, north of Wassenaar is
Lentevreugd (52.161299,4.392577), which is accessed from where the Katwijkseweg meets the Kokshornlaan. This site has turned up quite a few vagrants, and holds
Spotted Crake at the moment (don't count on seeing that though).
For something different, the
Noorderhavenhoofd and
Zuiderhavenhoofd in Scheveningen must still hold a few
Purple Sandpipers; there is usually someone seawatching here (
http://trektellen.nl/trektelling.asp?telpost=71&site=0&land=1&taal=2&datum=20110418).
