Sorry its taking so long for the 1-12 strategy but I've been a little busy (workin 12's).

I wanted to upload a video but I suppose a text explanation will have to do for now.

1-12: 55,100
The first bird I arced high into the air. I put him directly between the two blades of grass near the slingshot before I released him. Then I split him slightly after the top of his trajectory, at about the top of the screen. PRACTICE THIS SHOT! This is important. Done right you'll score over 18k and pop one pig. Done perfectly, you'll score over 20k points (in the record I scored 21k+) Even if the top pig lives and you score 15-16k, that's also fine becuase the next shot will easily kill him.

Now the reason the first shot is arced high, is becuase you want at least two (if not all 3) of the split birds to land and STAY on top of the wood blocks. Becuase the next shot is fired at the first wood block and split slightly before impact. I put this one at the spot where the background sky changes from dark blue to light blue.

But here's the kicker: this second shot must be made ASAP. As soon as I split the first bird, I immediately scroll back and fire the next bird. This is to maximize the chance that the first trio of birds wont dissapear yet and fall down to pop the remaining pigs while the second trio damages some more blocks.
That's why practicing the first shot is so important. It must be fired and forgotten, and then your next shot released soon after.

I'll try to make a video for later but for now I hope that helps.