To get this achievement you need to release the bird in Chapter 1 and find it again in Chapter 4
In Chapter 1 you'll need to get up a hill to get to the area with the rabbits and the sheep. Before you use the "hamster wheel" to Lower the bridge. There is a wooden platform with a parrot in a cage. Open the cage with the little brother.
In Chapter 4, when you arrive at the professor's "area", go down the stairs towards your objective you'll see a telescope. (This is before the hang glider!) I used the older brother, but think either will work. Interact with it and look to the bottom right. You'll see one bird sitting on a tree branch. Focus the camera on him and zoom in if needed to trigger a little cut scene and get the achievement/trophy.
You don't have to do this in a single play-through. If you free the bird in Chapter 1 in your initial play through, just use the chapter select to go to Chapter 4. If you now use the telescope the bird will be there and you can get your achievement/trophy.
I found a YouTube video that helps get this achievement. I didn't make it.