To make a homemade sparrow trap, cut a 8-by-12-1 inch cedar board to the required size for the trap's frame. Make the trap's elevator using a piece of cedar board, a plastic jug and a pill bottle. Finally, build the down chute.
To make the sparrow trap's frame, cut four 18-inch pieces from the cedar board. Halve two of these lengthwise for the top and base and the other two for two 18-by-10-inch front and back pieces. Halve a 10-inch piece lengthwise for the trap's sides.
Join the sides, back and top pieces to the base piece using wood screws. Attach the front using hinges, and add a latch to it.
To make the elevator, cut a 12-by-1 1/2-inch piece. Cut the ends of a 1-gallon plastic jug, and screw it perpendicular and centered on one of the piece's ends. Attach the pill bottle, with its mouth facing up on the opposite side and end. Attach two 2-by-2 inch planks towards the trap's bottom. Drill holes in the 2-by-2s to insert a steel rod. Place weights in the bottle.
To make the down chute, drill two 1 1/2-inch holes on the trap's front and back so that they are aligned with the jug's raised and down positions. Affix a PVC flange, elbow and a 4-inch wire mesh cylinder to the back hole to make a holding cage. Close the cage's open end, and cut a 4-by-4-inch square towards the bottom. Secure the square as the cage's door.