Aechmophorus grebes are often ambiguous between Western and Clark's, especially in winter; see two birds I photographed within a week of this one, http://www.pbase.com/tgrey/image/89421228 and http://www.pbase.com/tgrey/image/89191127 . This one looks to be pretty clearly a Western, with the lores dark gray and the eye well within the black crown. The relatively thicker bill indicates that it is a male.