I like how your bird doesn't just die instantly but loses some of the feathers (turning white with only the inner ones remaining) first.
It's a bit unclear to me what the different kind of enemies do, is there some significance for the parachute ones or the one in the plane, or are they just having different speeds and possibly scores attached to them?
It's actually surprisingly hard to fly in formation on the "normal" game mode and not lose too many of the birds too quickly, one has to avoid the incoming enemies quite a lot...