national aviary >> how's the water?

HUNTERS AND HUNTED
Some birds hunt other animals to get their food, while some have to be on guard against animals that want to hunt them. Can you tell the difference between a hunter and a hunted bird?

WHAT'S FOR LUNCH?
Who eats what? In this experiment you put out a variety of foods, and figure out which birds come to each kind.

BEAKS ARE TOOLS
Some good food can be hard to get at. Birds have evolved beaks that are very good at gathering their special food. Can you figure out what a bird eats by looking at it's beak? It's easier if you compare the beak to tools you already know.

BACKYARD BIRDFEEDER
Attract certain kinds of birds by putting out specific foods. We show you how.

DDT is a chemical that used to be sprayed on crops to kill insects. It's illegal in the US now. This picture shows how DDT harmed the Ospreys. Click on any of the five steps for details.

Demonstrate the surprising strength of eggs.

2 dozen eggs of equal size
4 egg cartons
hardback books of equal size and weight, at least a 2-foot stack

Ask the students if they know how strong is an eggshell. Write down the answers on the board.

Explain that you are going to squeeze an egg on either end and it will not break.

Students will estimate how many books can be stacked on top of four eggs.

Place four eggs of the same size in the second and fifth rows of an open egg carton, pointed ends down.

Carefully place one book, (one with a surface that you can wipe clean) directly on top of the eggs, and continue adding books, one at a time, balancing the pile as you go.

See how tall a tower you can make.

Discuss your results.

An egg's dome shape makes it resistant to compression. That's why a mother bird can sit on her eggs without breaking them. On the other hand, eggs and other dome shapes are weak in tension, a force outward, so that a baby bird can easily peck its way out when hatching.

Demonstrate and explain how chemicals can effect an eggshell.

eggs
cup or jar to hold eggs
vinegar

First complete the egg strength experiment.

Ask: How has DDT affected Bald Eagle and Osprey eggs. Place an egg in a jar or cup, and cover it with vinegar.

NOTICE bubbles forming on the surface of the egg. This is a chemical reaction between the acid in the vinegar and the calcium carbonate in the eggshell.

Leave the eggshell in the vinegar overnight.

Next day, examine: the shell will have gradually dissolved, leaving behind an egg inside a soft membrane.

Chemicals in an animal's food or water can cause strange things to happen. You saw how DDT affected the osprey's eggs. Now you will do your own study to see the effects of vinegar on eggshells.

Unsafe water can come from far away, and result in surprising things. The Osprey is a fish-eating bird that nearly went extinct because of farmers spraying their crops. How is that possible? Read on.

Click on A, at left, to start...