Sexual selection. Are ducks impressed by drakes’ display?
“Surprisingly few birds have penises, but among those that do,
the Argentine lake duck (Oxyura vittata) tops the bill – the
penis of this small stifftail duck from South America is shaped
like a corkscrew and, at almost half a metre long, is the
largest of any bird measured so far. Factors responsible for the
evolution of this remarkable organ could include runaway
selection, whereby drakes with longer penises gain dominance and
copulate with more females, or preference by females for drakes
with longer and more decorated penises.” “Most birds have simple
genitalia; males lack external genitalia and females have simple
vaginas. However, male waterfowl have a phallus whose length
(1.5->40 cm) and morphological elaborations vary among species
and are positively correlated with the frequency of forced
extra-pair copulations among waterfowl species. Here we report
morphological complexity in female genital morphology in
waterfowl and describe variation vag