Sudden extremes can act as hard boundaries, limiting where species can breed, feed, or recover.

POTTER, Neb. — When Reed Cammack hears the first meadowlark of spring, he knows his family has made it through another cold, snowy winter on the western South Dakota prairie. Nothing’s better, he says ...

This little songbird is native to the western United States, but has been introduced into the eastern side by man. It has become fairly common across most of the United States. The bird I show here is ...