As you can see in the picture that handy Andy has tried to pigeon proof an failed.
Its important to proof against possible problems regarding pigeons nesting and not to ignore it as it can lead to damage to your property . The issue is can lead to a health an safety risk giving the diseases associated with pigeons like E-coli, Ornithosis an when dry can become airborne an lead to psittacosis which is a respiratory disease
pigeon guano is also acidic an can cause damage where left. Pigeon proofing by professional pest controllers is key to prevent this happening