Friday, April 2, 2010
If you look closely at this male's vent, you might notice a pink, slightly curly structure. Since I have assisted Federal duck banders, I was aware that ducks and ratities (flightless birds like ostriches and emus) are the only birds with penises. (All other birds get the job done with a cloacal "kiss," with little or no penetration.) Tonight I discovered that I am mistaken, instead of a true penis, ducks and ratites have an erectile cloacal phallus. Sperm are deposited in the male duck's cloaca and travel down the outside of the phallus. In mammals, of course, sperm travel through the penis's interior in the urethra. Thus the two structures are not homologous.
You learn something new every day; in this case from Cornell Laboratory's Handbook of Bird Biology.
Posted by Dan Tallman at 7:44 PM