MIGRATION PATTERNS OF DOUBLE-CRESTED CORMORANTS EAST OF THE ROCKY MOUNTAINS

The 5589 recovery records for Double-crested Cormorants (Phalacrocorax auritus) banded in North America from 1923 to 1988 were analyzed to determine migration patterns and the source of populations wintering in the lower Mississippi Valley and Gulf of Mexico coastal region. Autumn migration from areas north of latitude 42°N primarily occurred in October and November. Spring migration occurred mainly in April for birds \u3e2 yr old and in May for birds \u3c1 yr old. During summer,1-yr-old birds were recovered significantly farther from their natal colony than were older birds. Cormorants nesting in Canada and the northern United States from Alberta to the Gulf of St. Lawrence migrated in winter primarily to the southern United States between Texas and Florida. There was considerable mixing and overlap in winter of nesting populations from widely divergent areas. From 38 to 70% of the birds from Saskatchewan throughout the Great Lakes region were recovered in the lower Mississippi Valley as were 10% of the birds from such disparate areas as Alberta and the New England coast. There was little mixing of populations from east and west of the Rocky Mountains