To get the bird-push, run up to the bird's platform as quickly as possible (at that Y-position, the bird starts walking Right). The Bomber will collide with the bird for a long enough duration to make the bird walk Down for 2 moves.
If you're standing too close, the bird will then walk Up more to meet you. So, assure the bird walks more Right, by standing at least this far away (note the stair above hair):
Farther away is fine, but you'll have less time after the Bomber passes you to actually run behind the bird. (As long as there are no pixels of the roly enemy still in your path, you're clear to move.)
If you run up behind the bird fast enough (cutting the corner even while the bird obscures it), you can de-spawn the final Bomber. Else, simply clip up past it.
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