Can we save millions of migrating birds?

In 1978, a young scientist “brazenly trespassed” around a Chicago building in search of dead birds. He unwittingly began a 40-year journey that could help save countless warblers, thrushes and more. Most of America’s 10 riskiest cities for migrating birds lie in the middle of the country. We’ll find out why — and how every resident from Texas to the Canadian border can help reduce the death toll.