Lob the first Blue bird so that one or two of the birds make it past the top of the left structure. Replicate the shot with the second Blue bird, so the whole right side of the level should be cleared. Finally, use the last Blue bird horizontally to push everything to the right. For more informations, see the first video walkthrough in this page.
Aim the Blues at the second hollow square stone block (counting from left to right) and split them just before they hit it. The half of the first structure will be pushed to the right and make the structure next to it falls and pop the pigs at the far-right. It's hard pop all the pigs after you do this so it usually needs one more bird to get it. If this happen, shoot the Blues to the far-right and pop the remaining pigs. For more informations, see the second video walkthrough in this page.