Ok, what worked for me, because I had a lot of trouble with it also, was to shoot all 4 birds basically straight at the first wall, then right before it hit the wall, tap the screen, dropping an egg AND rocketing the bird into the wall. With each successful bird, more and more wall blocks and wood pieces will disappear. It doesn't work every time, but do it enough and it WILL work, at least it did for me. Try that and see if you can get it to work.
I will not change my sig until one of the Cleveland teams(Indians, Browns, or Cavs) wins a Championship--Started(11-19-05) (EDIT...BFBC2 name: FarFromSober)
^ That's on the right track... My checklist goes like this:
Bird #1 gets fired into the left wall as described above (as you drop an egg right next to the wall on the two guys). This should kill the two guys on the left, as well as the guy next to the #1, and have the back of the car fall down. Sometimes you'll get lucky and the antenna will drop and kill one or both of the two guys on the right.
Bird #2 gets launched all the way over and drop the egg right next to the wall. this should kill the remaining bad guys on the right, as well as the one on top of the 2, the front of the car will go down here (if it doesn't, all is not lost).
Bird #3 gets launched the same way as the first one, drop an egg before the wall and have him launch up. This will upend the structure the car is on, killing the 'driver' and the guys in the 9
Drop Bird $4 on the 8 and they're gone!
This won't always go perfect, but this is a pretty consistent formula I think, I did this and got three stars, so I'd say it's worth a shot