Cloacal Protuberances

I last posted about some of the ways banders identify a bird's age.  Often both sexes of birds are similar.  The photo below is of one of these species, the Chipping Sparrow. In the photo, the bird is on its back, with the tail going towards the upper right and the belly feathers moved out of the way. 

 

When breeding, most male birds have a swollen cloacal protuberance, the structure in the center of the photograph.  A female's cloaca is, by comparison, never so swollen. Structurally, the cloacal protuberance is not a penis.  The swollen cloaca is also not a cloacal phallus (an organ of ducks and ratities), which I wrote about in my 2 April 2010 post.

The cloaca is a chamber into which empty the digestive tract (the anus empties into the cloaca; the exit of the cloaca is called the vent), sexual ducts, and urinary tubes.  Cloaca comes from the Latin for sewer.  Male birds get the job done with a cloacal "kiss," with little or no penetration of the female. I will have more to write about cloacae (I assume cloacae is the plural of cloaca) in my next post.