As I was walking thorough my neighbourhood I've noticed a cute blue bird silhouette, sprayed on a wall of a building. I thought:"nice :)" and moved on...
A week or two later, my friends and I were passing by a place called "Fantasy club" in the old part of the city. I've noticed that a little blue bird (different than the first one, but obviously made by the same technique) was on the wall of the place.
As I was pondered by the curiousity of the two silhouettes, I started searching for more of them across the city....

Who did it?
Why?
What do they mean?

I have no idea...If somebody knows the answer to this puzzle-please tell me. Also, if somebody has seen more of them; let me know so I could put them on the map.