Parrots have strong, curved bills that they use for feeding on seeds. The top part of the bill (upper mandible) is broad with ridged edges and tapers to a sharp point. The lower mandible fits snuggly into it and has cutting edges. Because the upper mandible is loosely hinged (rather than fused) to the skull, it is highly moveable. Working together, the mandibles make a formidable tool for cracking hard nutshells and removing the seeds. Besides seeds, parrots may eat fruits, insects, nectar, leaves, or pollen. Their fleshy tongue loaded with touch receptors helps them move food into and around their mouths. Some parrots have touch receptors lining their bills as well, giving them an unusual ability, among birds, to manipulate their food. Both their bills and their grasping toes allow parrots to climb around in the treetops and hang onto branches while feeding.