I would try Anti Bird Spikes:

• Protects potential roosting sites from pigeons and other birds, preventing them from soiling the area

 
• These spikes repel birds without harming them by acting as a barrier to roosting

That's only one example, surely they come in many different forms and colors, but the idea is the same.

I would try Anti Bird Spikes:

• Protects potential roosting sites from pigeons and other birds, preventing them from soiling the area

• These spikes repel birds without harming them by acting as a barrier to roosting

That's only one example, surely they come in many different forms and colors, but the idea is the same.