Catgut to stop Bird Poo ?

[STATUE]

I am moored on a river where both seagulls and pigeons poo all over my coachroof from the height of my crosstrees .
I am sure somewhere I saw a taught line a few inches above the crosstrees, no doubt from the stay to the mast.
Not wishing to trap the feet of birds, what should I use and at what height above the crosstrees?

 

[Concerto]

Fishing line would be my choice. However, some birds will land on rigging like these in Brighton Marina.

 

[Stemar]

Starlings?

If you find a way to keep them off - or even just to keep them from eating blackberries before they poop all over your boat, I've got a mate who wants to know it. They love his boat, but leave the other boats around his alone.

 

[MontyMariner]

Try clearing the deck after a Cormorant has shat all over it!

 

[STATUE]

Thanks Concerto - that's the way I'll go.