Level 1-1
Level 1-1 presents you with one giant green pig teetering on a rickety wooden structure decorated with two pumpkins and two lanterns. Even though you have four red birds as ammunition, you can clear the level and earn three stars with a single shot. Aim your first bird at the nearest hanging lantern to knock out the structure's left leg and send everything, pig included, crashing to the ground.
Level 1-2
One of the more unique levels in the game, level 1-2 features a series of pigs balanced atop pedestals that climb two large steps. You want to launch your first bird in a high-arcing trajectory so it hits the very last pig on the highest step. Your bird will pass through the pig, strike the back wall and ricochet into the pedestals, toppling all of the pigs like dominoes.
Level 1-3
A towering ice sculpture with a giant pumpkin at the top shelters four pigs on level 1-3, while a pyramid of ice cubes provides addition protection up front. As always, pay attention to the tower's lanterns to fix aiming points. Shoot your first bird, a little blue one, at the nearest hanging lantern, splitting the bird into three just before it hits. Almost the entire structure should collapse. Split your second bird so it blasts through the top of the ice pyramid to clean up any scraps.
Level 1-4
On level 1-4, you'll have three little blue birds and one red bird to take out four pigs hiding beneath a protective structure made of ice and wood. To earn three stars, simply use all three little blue birds to plow into the structure, tapping the screen a second before impact to split the birds into three. The blue birds are especially effective against ice, so they make short work of the pigs.
Level 1-5
Level 1-5 provides you with four yellow birds to eliminate two large green pigs in the base of a thick wooden structure and four little pigs and some pumpkins decorating the top. At first glance, the structure appears sound. But look at the three hollow wooden blocks positioned across the middle. Aim your first bird at the nearest hollow block and accelerate before impact. You should take out the entire left side. Now, shoot the second bird along the exact same path, accelerating at the end to bring down the rest of the structure and to crush the final few pigs.
Level 1-6
Five pigs use an impressive wooden tower with a couple of cement blocks for protection on level 1-6. You have four yellow birds to destroy the tower, but using only two will earn you three stars. Aim your first yellow bird at the nearest little green pig. Don't forget to tap the screen before impact to accelerate the bird. The collision will cause the structure's entire left side to collapse, likely squashing two little pigs. Next, fire your second bird at the level's lone big pig. If accurate, your shot should hit the remaining three pigs.