Commensalism
A Red-Tailed Hawk building a nest in a Saguaro Cactus is an example of commensalism in the desert. The Hawk benefits by getting a home and the cactus isn't harmed. The Hawk will live and hatch its eggs in these nests.
Parasitism
The Elf Owl building its nest in a Saguaro Cactus is an example of parasitism. The Elf Owl benefits by getting a home and nesting spot. The Saguaro however is harmed because of the hole made in it. The owl will nest here and sometimes even use it's hole to catch prey.
Mutualism
The Long-nosed Bat eating from flowers of the Saguaro is an example of mutualism. The bat benefits by getting food. The saguaro benefits by getting help polinate. The bats will come out at night and eat from the flowers.