Male chicken possess only a rudimentary phallic nub, which they use to pump their sperm into females using a ‘cloacal kiss’. The cloaca is the posterior opening which birds use for both excretion and reproduction. The rooster presses his cloaca against the female’s and squirts his sperm inside; on the other end of the penis spectrum, ducks have very long and elaborate penises, which measure about half of their body lengths.