You can make a plastic bottle bird feeder by cleaning a 2-liter plastic bottle and removing all labels, cutting two small holes at the base of the bottle, one small hole on either side of the bottle near the top and two more holes slightly closer to the bottle's top. Loop twine or wire through the two bottom holes, and place two wooden chopsticks through the holes closest to the bottle's top. Fill it with seed, and replace the cap.
The loop of twine or wire at the base of the bottle provides a way of hanging the feeder from a tree branch or other location outdoors. Wrap the twine or wire around the branch, and then secure it in place with a knot. The bottle hangs upside down, ensuring seed falls easily to the two feeder holes.
The chopsticks function as perches for the birds using the feeder. The two small holes above the chopsticks are feeder holes where birds can access the seed inside the bottle. The feeder holes should be no more than one-third of an inch in diameter, as larger holes allow seed to readily pour out of the feeder and onto the ground.
Experiment with different types of bird seed and different sizes of plastic bottles to attract different types of birds to your garden.