I’m trying to remove the Bird when it falls out of bounds
Cool! Start with any of the ten billion Youtube tutorials on bounds-testing, distance testing, collider / trigger testing, which ever method you want for your game. If you can’t make it work from a purpose-built tutorial, you absolutely won’t get it from this little box.
If you have a problem with what you already have above, then that just means… it is time for you to start debugging!
By debugging you can find out exactly what your program is doing so you can fix it.
Use the above techniques to get the information you need in order to reason about what the problem is.
You can also use Debug.Log(...); statements to find out if any of your code is even running. Don’t assume it is.
Once you understand what the problem is, you may begin to reason about a solution to the problem.