Ruff Calidris pugnax is a Palearctic lekking shorebird with three strikingly different mating morphs: aggressive Independents, semi-cooperative Satellites and female-mimic, Faeders. An autosomal inversion drives the development of the major morph differences in mating behaviours, ornamentation, and body size.

However, whether the morphs also differ in sperm traits has not been investigated. We thus use a captive-breeding population of ruffs to reveal how shorebird sperm propels and looks and whether the sperm velocity and morphology are morph specific.