It’s a fowl day on the East End. An outbreak of H5N1 bird flu has struck Long Island’s last remaining duck farm and forced the operators to put down 99,000 birds, according to reports.

Crescent Duck Farm, in operation since 1908, has over the past 70 or 80 years, “developed a meatier bird that has enough skin fat to make it really, really succulent when you cook it, without making ...