A nice, relaxing piece. I especially enjoyed the backgrounds, which added a sort of hand painted feel, and the music was also a very nice fit. It was both peaceful and sad in nice amounts, with a little bit of hope at the end.
However I would like to comment on your animation for the birds. The movements were not very fluent, and the part when the birds were in the park (I'm guessing that it was what that bird was hoping for it's egg right?), used a lot of still images, which I felt took momentum away from the finished product. When I comment on the movement, I'm not referring to the birds head movement, since that's how their heads move.
In short, a most awesome animation which fell short in terms of character movement.
On a side note, not effecting my review, what was up with that blob that lived in the tree?