Milk Carton Nest Boxes (with sealed lid) eFinch on Facebook
Made to mimic my standard wooden nest box, these milk carton nest boxes offer a cheap and disposable alternative. They are nearly the same size internally, but because of the paper walls are have a smaller external dimension which makes them ideal for small cages. The waxed paper will not absorb water from the droppings and then fall apart. I recommend placing some sawdust in the bottom to absorb some of the extra moisture to keep the nest from becoming soggy. When the birds are finished nesting, you just toss the whole thing in the trash and make another.

You'll need the following to construct this nest box:
• 2 quart milk carton
• Tape or double-sided tape
• Paper clip or other wire for hanging the box
• A knife or scissors to cut the box.

Start by cutting off the top of the milk carton right at the seam for the folds and spout. Measure up 4-1/2" from the bottom. Mark a line all around the container. Then, cutting down along the edges, cut from the top to the line. Do this for all four corners. Fold over one side 1" up from the line. This will form the back of the nest and provide a flap for you to hang the nest from.
Fold down the two sides that are next to the back at the lines. Fold down the front of the box on top of the other two sides. I tuck a piece of double sided tape under this piece, but some tape across the top would work equally well. For an opening, I usually use a half moon shape at the top of the box. You can provide what ever type of opening you and the birds like best. Punch a hole in the back tab and use some wire to hang the nest (click to view).
This style of nest box allows for a wide, half-open front. The wide opening is preferred by some birds and allows for easy access to the chicks for banding. If you need access to the chicks or eggs and prefer the hole opening, you may find that this style of milk carton nest box allows for easier inspection. (click here to view instructions on constructing this type of box.)
Milk cartons are not the only thing you can recycle to produce nesting facilities for your finches. Tin cans work well for many people and the birds don't seem to mind that it held peaches before their chicks. Salt cartons or oat meal cartons work also.

Use of household items is really only limted by your imagination.

Add a Perch - Take a large paper clip and bend a loop into the end. Stick a thumb tack or nail through the loop. Jab a stick onto the nail. Clip this on the opening of the nest box. The perch assembly is reusable after you throw the nest away.