Wash and dry the soda bottle. Cut 4 inches from the base with scissors. Then drill a hole in the bottle cap that you can fit the rope through.
Lubricate the inside of the bottle with the cooking spray to help the bird seed mold slide out easily. Then slide a length of rope through the bottle cap leaving 5 inches poking out of the cap and 12 inches coming out of the other opening.
Make the gelatin according to the directions, using ice-cold water so it will set up quickly. Add bird seed a little at a time to the gelatin and mix so the seed is completely coated and starts to bind together. (This mold used 2–3 cups of birdseed and a half packet of gelatin. Don’t use too much gelatin; the birds don’t like it.)
Fill the bottle with the bird see mix, using one hand to hold the rope in the center of the bottle and the other to pack the birdseed firmly in around the rope. When the mold is full, pack it down again. Place it in the fridge for a couple of hours to set, then take it out and let it dry for a couple of hours. When it’s ready, tap the bottle gently to release the seed. Taking off the bottle cap will help, and you can gently push from that end while pulling from the other end to release the shape.
At the round end of the birdseed mold, carefully unravel the rope to obtain two strands. Use the strands to tie the two dowels onto the bottom of the mold in criss-cross formation as a bird perch. Snip off any extra rope.
Drill a hole in the center of the wooden bowl. Tie a knot an inch or two above the flat end of the birdseed base and slide the wood bowl onto the rope upside down. Tie another knot right above the bowl and then make a large knot at the top for hanging. Snip any extra rope.
For more innovative how-tos like the Acorn Bird Feeder, check out the book "Design*Sponge at Home" by Grace Bonney.