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Cactus by Alex and Mark

We're Mark and Alex, and we're junior docents at the Arizona - Sonora Desert Museum. We do presentations for museum visitors about the plants and animals you can see here, especially the saguaro cactus. One visitor asked a question about the holes that are visible in the arms of the cactus: Do the holes in a saguaro cactus always face the same direction?

What did we do?
We walked out into the cactus forest to look at ten saguaros that have holes in them. These holes serve as nests for birds. We counted the holes, and made a note about which direction they face. We also looked for clues about what kinds of birds are using the nests.

What did we find out?
After looking at ten cacti, we found some holes facing in each of the directions. However, the most holes were facing either west or north. We figured this was because the holes facing west catch a nice breeze, and the holes facing north are shaded from the sun. This makes the nest more comfortable for the birds living there.

What can you do?
  • What kinds of creatures make nests in the trees near you? Compare the nests you see in pine trees with those in maples or oaks. Not all nests are made by birds, remember. Look for nests from squirrels, too. Are the nests always in the tops of the trees, or are some lower down? Are the nests located toward one side?
  • You can do an investigation to see if birds prefer to live in a bird house that faces the sun, compared to one that is in the shade. Build two bird houses, and place them in different locations. Watch in the spring to see which bird house attracts birds first. Do the birds in your area prefer a sunny house, or one in the shade?
  • Use this life science investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!
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