Hey! Thanks for trying out this game!
Here are some hints in getting other endings:
1. After you enter the first passcode and BEFORE you enter the next code on the bird: notice that one of the mosquito's eyes is a heart symbol. Find what the mosquito wants on the doll. If you feed it to the mosquito, when you meet the final boss in the red room, you'll have the option "Show me what true freedom is."
2. You're right on track about the bird! You have to not hurt it. So you'll have to paint the leaf with something else that's also red... maybe something that you have collected before and have not used yet. You can get two different endings from here: 1. you'll get a new option when you talk to the final boss 2. you'll get a different ending if you play the rest of the game the same way as you did for Ending 1.
Hope this helps!