Philomachus pugnax, commonly known as the ruff, is a bird species found in wetlands across the Northern Hemisphere. Synonyms for this bird include the fighting ruff, pugnacious sandpiper, and the reeve. The name "reeve" refers specifically to the female of the species. These birds are known for their elaborate courtship displays during breeding season, including the male's distinctive collar of feathers, or ruff, which can be raised and lowered in order to attract females. Other synonyms for Philomachus pugnax reflect their unique appearance and behavior, such as the long-legged sandpiper and the wading bird with frilled collar.