Bird annoyance

I have an issue with birds taking a dump on my metal porch railing. They must do it when I'm at work because I never see them. But once a week in the summer I have to clean the white crap off my rails. Not a ton of it each week, but enough to create issues. Any thoughts? Bird spikes are about the only thing I can think of. That or maybe put out 1 of those fake owls from Wal-Mart. They also sometimes kinda sit on the porch lite and make a mess. I suppose it would help if I knew what kinda birds they are.

Optical gel from bird barrier

http://www.birdbarrier.com/category/190TFOG/bird-barrier-optical-gel/

Interesting looking product. Wish I had know about this earlier. Have you used this product with success?
Also can this product be demoed to show the UV light flame? Thinks that would be the deal sealer there, if it can be.