Rook raiding hen and duck house.

A couple of rooks are stealing eggs from both our hen and duck house. The duck lays in the morning so its easy to remove the egg first thing. However we have 10 hens (a few moulting) and we are only getting 1 or two eggs per day.

We find the odd broken shell/egg, but not as many as we are missing. I often come home or out my back door and the rooks make a hasty exit.

Anyone come accross this before?
Would the rook be able to remove the whole egg?
How do i scare off the rooks? I can't close the house or the hens can't get in to lay!
Is is likely that the hens know the eggs are being nicked and are laying elsewhere?

Help, i sell the excess eggs to pay for feed, and the rooks are eating my profit!!

you could try putting strips of material at the pop hole entrance (like what we can have at our door way to keep flies out) - this is believed to work.