Why do presidents pardon turkeys before Thanksgiving?

Gobble and Wadd were the lucky turkeys receiving presidential pardons today. >> Are hereby unconditionally pardoned. >> But they were not the first.The National Turkey Federation started gifting turkeys to presidents of the United States. Back with Harry Truman in 1947. John F.Kennedy gave the first unofficial turkey pardon in 1963. He sent the bird back. But it was George HW Bush in 1989 who did what we would think of as the first formal turkey pardons which have become such a tradition at the White House ...