When a friend of mine told me about a bird having some fun snowboarding on a jar lid, I thought she was joking and didn't believe her. But now I'm pretty sure I've seen everything.
The windows in our building have some kind of reflective coating on them. They are almost like a two-way mirror in NCIS when Gibbs is interrogating someone. The reflection is so good that birds think they are going to land on a tree right next to the building when they are actually crashing into the window...