Tips to stop cat peeing on window sills?

[MrsBertMacklin]

I think BertCat is peeing on the sills while watching birds. No chance of it being related to seeing other cats, as we're on the third floor.

Any ideas about how to stop her, without depriving her of chattering at birds, please?

When my cats were old and started weeing in a particular spot I put a piece of kitchen foil on it and they avoided it. It would probably mean that she avoided the window sill though.

It perhaps could be that she's seeing/smelling other cats, their senses being so much keener than ours.

A Feliway plug-in may help?

Thanks both.

I threw away the Feliway after realising it sends her loopy, oddball that she is.

I've cleaned using an enzyme spray, fingers crossed!