This project takes about 30 minutes, only uses common household waste, and requires only basic skills. At the end, you will have a bird feeder and become a friend to the birds in your neighborhood.

Step 1: Bill of Materials

You will need the following materials:
2 liter soda bottle (other sizes work well also, but 2L is a good volume to hold seed)
1 gallon or 1/2 gallon plastic milk jug
~9 feet of hanging material (I used a bike tube because it was handy, string, wire or others will work)

You will need the following tools, or suitable replacements:
Scissors (should be heavy duty enough to cut plastic bottles)
Awl (or other hole-punching tool)

Step 2: Preparing Bottles

Soda Bottle:
Cut the bottom two inches of the soda bottle off, then cut four slits around the rim of the top piece so that the bottom can be placed back on, over the top (see assembly pictures). Then cut four small holes/slots in the top of the bottle for the seed to come out.

Milk Jug:
Cut the top of the jug off at the shoulders (where the sides start to slope up to the spout), leaving slightly more of the handle for something to hold on to. Next, poke three holes around the new jug piece, evenly spaced, not too close to the edge. Make sure your holes are going to be small enough to hold the hanging pieces from slipping through.

Bike Tube:
If you are using a bike tube, cut out a length about 3 feet long, then cut it open so you have a long rectangle of rubber. Now cut three strips down the entire length, about 1/4 inch wide. You will use these to hang the feeder.

Step 3: Assembly of Feeder

Attach the bottom of the soda bottle back on to the top (this will be the lid that you open to add bird seed). Don't put the two soda bottle pieces together too tightly, just enough so that a bird, squirrel, or strong wind won't easily open it.

Now poke the rubber strips through the holes in the milk jug and tie a fat knot on the other side (when using rubber, almost any knot should be fat enough, just make sure it will hold). Slide the milk jug piece over the cap of the bottle (the bottle and jug I used fit perfectly, but if yours is a little bit loose, you might need to fill the space with something to keep the seed from falling out).

In order to keep the feeder from flopping over, you will need to tighten the strips on it by tying a small ring of rubber around the three lines to cleave them together. To fill/refill the feeder, this ring will simply slide up and allow you to open it.

Step 4: Install Feeder!

Fill the soda bottle with bird food (available at many supermarkets for not too much $), find a hook, ledge, or tree branch and hang the feeder upon it. Preferably, this hanging spot will be in a visible spot (out a window), and easily accessible to birds and you (for refilling purposes) but not squirrels (they will eat from it no matter what...). Then wait for birds to come! Nice job on a project well done.