Squeaky building

There is a big fancy new office opposite my building. As you approach it, you can hear a strange squeaky chirping noise emanating from the entrance canopy. It's just like the noise a nest-full of chicks make when mummy bird returns with a beak of squished worms.

The first time I heard it, I assumed it myst be a nest. But it's now the middle of winter and the noise is still there. Perhaps it is some kind of bizarre pigeon deterrent...?