In late winter large numbers of migrating waterfowls appear at Middle Creek (a Wildlife Management area located in Pennsylvania) before heading north for breeding.   Many of the waterfowl come from south of Pennsylvania and begin their trek north in conjunction with spring thaw.   When the ice begins to thaw so there is open water and the snow melts from adjacent fields for the birds to have waste grains, they begin to arrive.    This year — the highest numbers started around the 17 March:   Snow Geese:  60,000+; Tundra Swans:   5,000+ and Canada Geese:   3,000+   These pictures are from 20 March 2014.