The beak of the greater flamingo (Phœnicopterus roseus) is suitable for filtering the silt from ponds and marshes. Its upper mandible is mobile and has small, horny, tooth-like growths. Its lower mandible, for its part, is fixed and lined with fine lamellae. When the upper mandible approaches the lower one, they together form a filter that retains the larger particles contained in the liquid mud that the flamingo circulates by rapid movements of its fleshy tongue.