Can Space Eagles be earned?

In Angry Birds: Space, can you earn Space Eagles without purchasing them? The Game Center achievement reads like you have to purchase them, and there are other achievements tied to the Space Eagle. I'm wondering if you have to purchase them to complete the other achievements tied to the Space Eagle.

Solution 1:

Yes: So far I've earnt 6 space eagles (in batches of three each time) through gameplay/3 star levels.

I've currently completed up to 2-11 and they did seem to come at major points: first unlocked golden egg/ 10 worlds and after the first boss fight.

Solution 2:

You get 10 eagles for getting 3 stars for every level in the first chapter, I assume you would get the same for the others