Biologists have long debated why some plants and animals can adjust to a wide range of climates, while others can't.

That's helped alter the kinds of birds people see in their neighborhoods. Take the eastern bluebird, which used to migrate north as the weather warmed up. Now they're common and abundant in ...

That's helped alter the kinds of birds people see in their neighborhoods. Take the eastern bluebird, which used to migrate north as the weather warmed up. Now they're common and abundant in southern ...