lydia said..
Here is one that has worked for me at least in the cockpit and under sail if left on the boom.
Buy a pack of pool chlorine tablets
Put a tablet on a small bucket or container with holes in the sides.
Hang under the boom.
Pack away in later sealed bucket when on the boat.
No guarantees but some birds don't like the smell it seems
You're onto something there, when we paint any major part of our boat, the birds won't touch it for a few weeks.
Dad experimented with vixen in a container that would let the smell out but not the water in.
Seemed to work for a while but they got used to it