Cockatiels are odd little creatures at times, and it isn’t always easy to understand their behaviors.
We form deep bonds with our birds over time, and their behavior ultimately shows us just how deep those bonds run.
The image of a parrot sitting on the shoulder of a person is one that is centuries old—but why exactly do cockatiels like doing this?
Parrots in general form a bond with your face in particular. There are some theories for the precise reason they sit on your shoulder, but it’s believed they get the sense of sitting with you as they would on a branch. They almost territorialize your body. It also just allows them close to your face.
So, the simple answer is we don’t know for certain.
However, it seems like a good bet that it is to do with how they bond to our faces, and how they end up seeing your body as somewhere that belongs to them.