In the Central Valley of California, a cornfield is hosting a huge swarm of tree swallows, between half a million and 1 million of the songbirds, who are on their way south for the winter. Bird watchers have flocked to the cornfield where the birds feed and sleep, calling it only the third large-scale roosting site for tree swallows west of the Rockies. No one knows how long this historic sighting will last as the birds plan the next leg of their trip, traveling as far as Central America, where they may be filming a remake of this film classic.