Reprinted, with permission, from "Sialia" (Summer 1998) Journal of the North American Bluebird Society. NABS is a membership organization for persons interested in bluebirds and other North American birds which use cavities for nesting. For membership information, send a message to nabluebird@aol.com or go to the NABS web site at http://www.nabluebirdsociety.org/