The greater flamingo (Phœnicopterus roseus) has several feeding techniques. It can move slowly through the water, digging the bottom with a sideways movement of its submerged head, or it can stand still and rotate around the axis of its legs, exploring the mud with its beak. The shape of the flamingo's beak is such that when its upper mandible is in contact with the muddy bottom, its lower mandible is paradoxically placed above its upper one. It then sucks up the liquid sludge filtered through the lamellae of the beak to retain only the nutrients.