How do I free the bird from the cage?

First, you'll need to find a way to get up to the cage.

Do you see that rope that runs near the bird cage?  You'll need to use it
to carry you up to the cage.

The rope is very long.  It runs all the way to the left side of the screen.

You need to use one goblin to pull up the other with the rope.

First have one goblin hold onto the rope near the bird, and then have the
other pull the rope on the left as soon as possible.