Feces of Birds

Our living apartment has been 10 years passed after building. Therefore, repair works was done recently. And now is over.
After repair works, some bird comes to my room’s veranda. Why I notice it? Because they leave their feces. It makes me unpleasant feeling.
How to do for birds never to come? Some people use some CDs. Because birds dislike flash. But in my veranda, it’s difficult to put CDs because when wind blows, they will be blown off.
So, I wrap veranda’s in handrail some aluminum foil. I hope that birds never come.