During the earths last glacial maximum an ice sheet separated the Swainson's Thrush on their migratory path. The two groups of birds were separated for so long the they became different subspecies, The olive backed and the russet backed Swainson's Thrush. The glacier has long since melted but the ghosty outline of the glacier is traced every year in the migratory paths of the two groups of birds. Mark Denny the author of the book "Long Hops" lends his expertise to this short film by Coulter Stuart and Green Globe Films. Original art by Bonnie Lalley.