I just searched for 'Ruddy Duck cull' on the RSPB website while looking for the latest information amongst various sources. Here are the results...
Searched for 'ruddy duck cull'
Results 1 - 2 of about 9.
Did you mean: ruddy duck call
You know, I don't believe I've ever heard one vocalise... apart from the bubbling display of the male which is really mechanically produced. Maybe they do call, just as they are knocked out of the sky. As long the species is kept in wildfowl collections in the UK it is unlikely to ever be completely eradicated. Click here for a nice photo of some ruddies.