For centuries the snow goose has signified the passing seasons to the Indians--its white feathers a symbol of the breadth of life and a reminder of the roles the birds played as messengers between heaven and earth. The importance of the geese in these roles is attested by their prominence in Indian lore and myth. As a boy growing up in North Dakota, Paul A. Johnsgard measured his winters not by conventional time units, but in the days it took for...