With a clear dishwashing-liquid bottle and a few plastic straws, you can easily make a hummingbird feeder and demonstrate the effects of atmospheric pressure at the same time. The clear bottle works best because the birds will be attracted to the red color of the sugar water as well as to the water's scent.
What You Do:
- Wash out the dishwashing-detergent bottle thoroughly to remove all traces of detergent. Keep the squeeze cap - you'll use this later.
- Have an adult help you punch four equally-spaced holes near the bottom of the bottle, using the nail. If your bottle is squarish, punch two holes on each opposite side.
- Enlarge the holes with a sharp pencil, but insert the pencil at a steep angle (toward the bottle's bottom) so that the hole becomes somewhat oval-shaped. This shape is necessary for inserting the straws at an angle.
- Cut the two straws in half, and carefully insert all four pieces into the holes you just made. Push each straw two-thirds into the bottle, making sure that each straw angles up.
- To keep the hummingbird feeder from leaking, apply epoxy glue where the straws enter the bottle. Allow the glue to dry overnight.
- For the solution, mix 1 cup (240 ml)of sugar in 2 cups (480 ml) of water.
- Before you begin filling your feeder, place it over the sink. Insert a funnel into the mouth of the bottle.
- Quickly, but carefully, pour the solution into the feeder through the funnel. The solution will begin to spill out through the open straws until you replace the closed squeeze cap.
- Secure the cap tightly and tie string around it. Hang your finished hummingbird feeder close (but not too close!) to a window where you can enjoy the show.
The solution travels to the tips of the straws but does not spill out. As the hummingbirds feed, more solution travels from the bottle to the straws without overflowing.
A hummingbird feeder relies on atmospheric pressure to keep most of the liquid inside the bottle and just enough at the tips of the feeder pipes to attract hummingbirds. Before you replaced the cap on the bottle, more atmospheric pressure acted upon the liquid in the bottle than on the tips of the straws, and so the solution overflowed. But by securing the cap on the bottle, pressure inside the bottle was lessened so that the greater pressure came from outside.
Excerpted with permission from 100 Amazing First Prize Science Fair Projects by Glen Vecchione (Sterling Publishing Co., 1998).