Really cool. The game was indeed very difficult, so I played a bit and then watched the playthrough, but I think I'll try playing it again at some point and getting further on my own.
It's very well done, the mechanic with the birds is original and works pretty smoothly, and I liked the graphic style very much (the Hitchcock reference really added to the mood).
Some notes:
1. You have a "tutorial" of sorts in the beginning where you see text explaining some of the basics of the game, but even at that early point it's easy to die, and that interferes with the tutorial a bit. I only realized later that the first bullet gun only shoots to a certain distance, it's a bit weird how the bullets just disappear at a certain point.
2. The text "Remember, if you run out of bread, kill yourself or switch checkpoints" - this wasn't so clear and it took a while for me to realize that getting a new checkpoint also replenished the bread.
3. When riding birds, I think it would be cool to change the character so he looks like he's actually sitting on a bird, this way they'll look less like moving platforms, and you shouldn't be able to fall off them.
4. A better visual cue for entering the boss fight (indicating that you now have unlimited bread) would help. Also, the text about the birds not being able to get through the shield confused me - makes it sound like they aren't actually doing him damage.
Loved the ending.
This feedback is on very specific things since overall I thought the game was great, very impressive!
P.S. Didn't rate on Humor since I don't think the game was supposed to be funny.