If you have any old Video/VCR tapes, or old cassette tapes, unwind the tape from it and suspend large lengths from anywhere high in your garden, like your line, walls, any poles. Also use plastic bags, as the look and noise from both scares them.
Be sure there is no food sources for them around, like pet food left out, or discarded food from kids, etc.
I have a similar problem with birds these mornings too, jackdaws or some other croaky cawing bird calling over and over from 4am onwards. This is especially a problem these nights when I'd like to leave the windows wide open to let a little air in.
So when I saw the above post I thought- brilliant idea, must google that in ireland to see where I can get one- but all that came up was your post!