Thunderbird eccentric by modern flitknapper collected from Collins Collection. The thunderbird effigies are usually made by Native Americans, unique to the Northern Plains Area from 1,000 to 1,500 A.D., and used within the ritual or ceremonial realms of use. Eccentrics are the finest chipped artifacts from flintknapping that take shape of several symbolic designs. They are not used in daily life, but more commonly known to be used in ritual events. The Mayan culture eccentrics are some of the most notable and spectacular discoveries within Archaeology.