Remove milk residue from an empty milk carton by washing the carton. Allow time for the carton to dry completely and then make a hole from the bottom of the carton to two or more of its sides. Make sure that the side holes are at least three inches in diameter so that the birds can reach the food easily. Make another tiny hole for water drainage.
Paint the milk carton by rolling it on all sides in a plate containing the desired colour of non-toxic paint. Be sure to cover the work surface with a large piece of newspaper. You might have to apply more than one coat of paint in order to ensure that no area of the milk carton remains visible. Be sure to allow the first coat to dry completely before applying the next one.
Add the seeds that you want to feed to the birds to a plastic bag and then cover a bagel with peanut butter on all sides. Place the bagel into the plastic bag and then seal off the plastic bag. To make sure all sides of the bagel are coated with seeds, vigorously shake the plastic bag.
In order to hang the feeder, poke a tiny hole through the top of the milk carton and then feed a piece of strong string through that hole. Tie the string in a double knot.
Place the seed-covered bagel in the carton after removing it from the plastic bag. Fill the carton by adding the remaining seeds. The bagel you added will serve as an additional bird treat, and prevent seeds from falling out of the milk carton through the holes you made earlier.
Secure the feeder to the branch of a tree by means of a double knot. Make sure you pick a branch that is strong and sturdy enough to handle the weight of the bird feeder and the birds that will be attracted to it.