I managed to get all 84 birds, so if anyone is stuck feel free to post a screenshot and I'll tell you how to get it.
As far as I can tell, the pink square in the topmost left room doesn't do anything, but it seems strange that it's the only instance of that sprite. Also feels weird that nothing happens upon fining the 84th bird. Am I missing something here? Please let me know.
Spoilers below on how each tool works, plus tips on using them:
- Pressing the drop button for any tool will always use it on the block in front of you, "front" being determined by the last direction you took a step in.
- Jump always takes you to the center block in any room. Use this to you advantage to reach puzzles from the other side without resetting or to get across barriers.
- Boats let you sail across water or teleport to rooms that have water in the center. Jumping/teleporting while in the water will change the boat into a droplet.
- Droplets can be dropped on the ground to create water. They can also be placed on the pink mushrooms to create birds.
- Frogs fall into water if they are on a block directly touching it in a cardinal direction. Diagonally-adjacent blocks are frog-safe.
- Swords break crates.
- Books change skulls into birds.
- Donuts immediately attract all pugs in the room to run along the shortest available path to the donut once it is dropped. Pugs will not move until a complete path is available. You can carry in a donut from another room to use two donuts together for some puzzles.
- Getting a pug or frog to stand above a boulder will turn it into a bird.
- Typically you need to be on an adjacent square to a bird in order to "watch" it, but some birds have a larger range.