The white Pekin duck, often sold under the name Long Island duckling, are the ones most often available in supermarkets today. Broiler or fryer ducks are young (under 8 weeks) and tender, roaster duckling (under 16 weeks) is starting to harden, and mature duck has tougher flesh. The leaner Muscovy variety, a red-meat duck, can be found in butcher shops. Duck can be bought whole or as single breast fillets, called margrets.