This occurs in Act 6 Curtain 2. As you go up the tower you'll see pigeons, and a pigeon in the bird house. You need to use pikirina to hit the bird house and then you'll play a little version of an old shooter, the birds will come down in a wave and do two loops. Shoot them (with pikirina) and make sure they don't leave the screen. If they do, kill yourself (til you have no heads) and try it again
When that's done continue up the tower and you'll see a second pigeon house, do the same thing to that house (knock on it) and this time two groups of pigeons will fly out doing a loop. They come together in the middle which is where you should try to kill them. If you kill you have killed both groupings you will unlock this trophy.