Peregrine falcons are rare birds. However, they are spread over a wide
area. They can be found on six continents. In North America, they live
mainly in Alaska, Canada, and the western United States. Some species
migrate to South America for the winter. Wherever they live, Peregrines
prefer a cliff or a rocky ledge. There, they can build a safe nest. These
homesites also provide a good hunting ground. The main idea in this
passage is:
A. Where Peregrine falcons migrate to.
B.How Peregrine falcons hunt
C. Why Peregrine Falcons are endangered
D. The habitats of peregrine falcon

The passage is about the habitat of peregrine falcon. It is said in the passage that peregrine falcon though rare, can be found in all continent of the world ranging from Asia, Africa, north America, Europe etc.

Peregrine falcon live mainly in Alaska, Canada, and the western United States even though they are found everywhere in the world. They usually build their nest on a cliff or a rocky ledge.

Therefore, the author's main idea of the passage is to describe the habitat of peregrine falcon, a rare bird.