The expression 'Πιάνει πουλιά στον αέρα' is used in every day Greek in order to describe a person who is extremely clever and competent in whatever he/she is doing. For example, it is used to describe bright students, competent scientists and many more. Although the origins of the expression are not known to us, one can easily deduce why and how the expression was created.
Catching birds in motion while they are up in the air is a difficult if not impossible task that requires a lot of accurate calculation, art, swiftness and skills among others. It is usually something that only the most competent hunters amongst the animal kingdom can do like for example, an eagle. Therefore, it can be easily understood that when referring to a person, it means that such a person possesses a paramount efficiency and intellect. So, do you know anyone who catches birds in the air?