Duckling predation

With reference to the previous posting, is there any evidence that gulls are responsible for predation of ducklings and cygnets in the area?

 Surely there is a wide range of avian and mammalian predators of ground nesting birds, of which gulls are merely a small part.

I remember a talk at last year's Welsh Ornithological Society Conference which debunked the myth that gulls are the baddies of the bird world.  It's a pity that Dave Purdon wasn't there. 

Personally I do like gulls very much and wish them every success.