The Passenger Pigeon's Flight to Extinction
One hundred years ago, the last passenger pigeon, named Martha, died in captivity at the Cincinnati Zoo. Not long before Martha died, passenger pigeons flew in packs so large over the U.S. and Canada they could block out the sun for days. Mindy Todd talks with author and naturalist Joel Greenberg about what lead to the extinction of the passenger pigeon and what it teaches us about the importance of conservation. He is the author of "A Feathered River Across the Sky: The Passenger Pigeon's Flight to Extinction".