I adore the visuals and atmosphere of your game! This is a great implementation for the theme, great work! The hummingbird controls really well with just enough inertia and the sense of speed is thrilling when flying at full speed, while still allowing a good level of precision when you need to.
I would allow the player to fly out of the nest as soon as the game begins, the controls explanation takes a bit too long especially after dying. Sometimes I had trouble gauging the hitboxes, those huge shadows on the foreground mask a good portion of the useful gameplay space. Making them semi transparent when you are behind them could help, maybe by using dithering instead of simply setting the sprite opacity, to preserve the retro look of you game.
All in all, great game! I didn't find your submission page, did you miss the deadline?