I thought I would add some more Lesser Scaup pics just to show some of the features a little more clearly.
Above - Male wing pattern again from underside this time. Oh, and the head shape is a belter even though the photo is blurred.
Above - Male size comparison with Tufted Duck, and the Lesser does indeed look smaller.
Above - The male, yes all the same bird showing, from the top, the differing head shapes according to whether diving or not. Note the coarse vermiculations on the mantle / scapulars against the very fine grey flank markings.
Above - Bill pattern, darker grey at base becoming paler blue grey towards tip with black nail.
Above - Female showing two head shapes one flat after diving, one 'field guide 'shaped.