This can mean a lot of things, depending of the context of the phrase.
For example:
- "Pajarillo" in the phrase - Se te ve el pajarillo ( We can see your pajarillo ) -, means penis.
- In the phrase - Tienes pajarillos en la cabeza ( You have pajarillos in your head ), means birds, wich is a figurative way of saying that someone is clueless.
