Learn Spanish (Latin America): Quiero liberar al pájaro en cuanto pueda volar. - I want to release the bird as soon as it can fly.

The phrase en cuanto means 'as soon as'. Because the bird cannot fly yet, its ability to fly is an anticipated future event. In Spanish, when a time-related phrase like en cuanto, cuando, or hasta que refers to an event that has not happened yet, it must be followed by the present subjunctive.

Wait, I am the one releasing the bird, but who is flying?

The bird is the one flying! In the first part, Quiero (I want) has 'I' as the subject. In the second part, pueda volar (it can fly) refers to the bird. The subject changes after en cuanto, which is perfectly fine. The verb pueda is conjugated for 'it' to match the bird.

Why is it al pájaro and not just el pájaro? Birds are not people.

You are spotting the 'personal a' combined with el to make al. While it is called the 'personal' a, it is also commonly used for specific animals that the speaker cares about or is individualizing, such as a pet or a rescued bird they are nursing back to health.

Could I use cuando instead of en cuanto here?