As summer turns to fall in North America, millions of hummingbirds migrate south to warmer climes. More than a dozen species of tiny hummers are on the move through the end of October. Flying from as far north as Canada, they can end up as far south as Central America. The colorful daredevil fliers need a lot of sweet nectar - natural or artificial - to fuel the journey. At 12:15 p.m. CT (17:15 UTC) on Thursday, September 18, ornithologist Sheri Williams joins EarthSky’s Dave Adalian to talk abo