Twice a year the wild birds migrate a hazardous 4,000 km (2,500 mi) from their nesting grounds in Wood Buffalo Park to the Aransas Wildlife Refuge on the Texas coast. The possibility of a major storm or devasdisease striking this flock is a threat which makes biologists shudder. One of the basic rules in the management of an endangered species is to spread the risk. A daring experiment was undertaken with the whooping cranes. Eggs were removed from nests in Wood Buffalo Park for artificial incubation and place-ment under setting sandhill cranes, a related, more plentiful species. The artificially incubated eggs are hatching and producing birds that are raised in captivSeveral whooping cranes have been hatched and are being raised by their foster parent sandhills in Idaho. If the experiment succeeds, a new flock of whooping cranes will have been produced, one which migrates a much smaller distance, over a different route, than the original group. A fringe benefit of taking eggs is that it stimulates the female bird to continue laying, thus generating more than the usual number of clutches per year. The most common grazing animal of the American coniferous and deciduous forests is the white-tailed deer. In the far West, it is replaced by the mule deer. There are actually more deer now in North America than when Europeans first arrived, because of the clearing of forest land, plus game management.

Bears once occurred throughout the forests of America north of Mexico. The world's largest is a brown bear, the Alaskan or Kodiak. The grizzly, also a brown bear, has been known to launch unprovoked attacks against humans.

American black bears are quite common in much of their range — practically all the wooded areas of North America north of central Mexico. They usually occur in their familiar black color phase, but also have been known to be a cinnamon color, brown, and even blue. The rare blue or glacier bear occurs only in southeastern Alaska, where there are about 500 left.

South of North America's taiga is the immense grassknown as the Great Plains. This covers most of the continent's interior and stretches 3,900 km (2,400 mi) from southern Canada deep into Mexico. It is prairie country, a seemingly flat land, devoid of trees exceptalong the river courses. Almost all of the original grasses were plowed under for the raising of crops, and of the tremendous number of wild animals which once lived there, practically nothing remains. As the naturalist Peter Farb wrote, "Not even the eastern forests have suffered the almost complete destruction that European man has brought to the grassland."

The story of the American pronghorn, the only "annative to the New World, illustrates his point. When Europeans first settled in the Western Hemi, there were an estimated 50 to 100 million pronghorn on the plains. Four centuries later by the turn of the 20th century, only 20,000 were left. Today, through strenuous conservation efforts, the prong-horn is safe, although consigned to a small fraction of its former range.

Another example of what happened to the plains' wildlife concerns a "dog." Before the Europeans came, hundreds of millions of rodents, called prairie dogs because of their dog-like call, lived in underground "towns" from southern Canada to Mexico. One such system of burrows in Texas covered more than 65,000 sq km (25,000 sq mi) and contained approximately 400 million animals. With the coming of civilization, the burrows were plowed under and the animals poiFew prairie dog towns still exist.

As the prairie dogs disappear, they are taking with them at least one of their predators, the black-footed ferret. This member of the weasel family has prairie dogs as its prime food. It has become overspecialized and is caught in an evolutionary trap.

North America's arid areas occur in the southwestUnited States and parts of Mexico. Large grazers and browsers include bighorn sheep, mule deer and javelinas, also called peccaries. Hawks, foxes, owls, coyotes, and several species of reptiles are among the carnivores. Among them, the coyote is one of the few which has thrived in the face of human intrusion into its habitat. Not only has it maintained its former range; it has expanded it.

One of the resident birds of the North American southwest is the roadrunner, a member of the cuckoo family. Primarily a ground bird, it can run at speeds of up to 24 kmph (15 mph). Its diet consists of lizards and other reptiles which it kills by repeated blows from its heavy beak. If prey proves too large to swallow, the roadrunner ingests a bit