A Bird Call using rubber bands (cordage and grass can also be used). Use a green branch, With a knife split the branch and remove a bit from the center of each half so you can blow through it. you can also remove the bark if you want.
Step 1: Name This Instructable
Use one band to hold a cut wider band at one end of your branch. Cover hole with your mouth and blow. Pull on rubber band or grass blade to change notes.