Why does the author include paragraph 4?

The whooping crane is the tallest bird in North America. It can stand nearly five feet tall. It has snowy white feathers, a red patch on its head, and black tips on its wings that show when it flies. Its name comes from its loud call, which can be heard from far away.

Every fall, many whooping cranes fly more than two thousand miles from their nesting grounds in northern Canada to the Texas coast. They spend the winter in the salt marshes of the Aransas National Wildlife Refuge and the land around it. There, they wade through shallow water and eat blue crabs, clams, and berries.

Whooping cranes once came very close to disappearing. Many of the wetlands where they lived were drained to make room for farms and towns. Many birds were also hunted. By the early 1940s, fewer than thirty wild whooping cranes were left in the world.

People worked hard to save them. Laws protected the birds from hunters, and their winter home on the Texas coast became a protected refuge. Scientists began counting the cranes every winter to see how they were doing. Slowly, the number grew.

Today, there are several hundred whooping cranes in the wild. They are still rare, but each winter, visitors to the Texas coast may be lucky enough to see these tall white birds stepping slowly through the marsh.