The intact C33-C52 diester wax esters of the preen gland of the shorebirds Limosa lapponica, Pluvialis squatarola, and Pluvialis fulva were determined, using synthesized standards, to comprise predominantly C12-C16 beta-hydroxy fatty acids esterified with a C8-C18 fatty acid at the beta-hydroxy position and with predominantly C12-C20 fatty alcohols esterified at the carboxyl group.