Every spring, billions of small migratory birds travel thousands of miles across North America, flying from Central and South America to summer homes as far away as Alaska. Then, weeks later, they turn around and head back South. This chaotic spectacle first captivated Kenn Kaufman as a teenager, when he hitchhiked across America on a yearlong bird-watching trek. Today, he's one of the most respected naturalists in the country. He joins Kojo to discuss the frenzy and beauty of spring bird migrations.