Of the roughly 10000 species of birds in the world only 3 percent of birds have a penis, 97 % have a cloaca (in ancient times cloaca meant a sewer) instead.
Of the 3 percent the ratite family (ostich, emus and rheas) have a penis. The male ostrich inserts his penis into the females cloaca (a waste and reproductive orifice) and sperm is transfered that way.
In most birds that have a cloaca (which is a small lump), during the breeding season as the hormones flow the cloaca swells and birds grow a cloacal protuberence.
When you next watch birds mating you will see it only lasts between one and three seconds. The cloacas are pressed together in a cloacal kiss and sperm is then transferred from the male to the female. It’s quantity rather than quality as they mate many times.
Ducks have an explosive spiral penis which is quite extaordinary to watch as it spirals out of the bird’s body! So the next time you see an ostrich or a duck you are seeing something rare in the bird world.
On the subject of penises, let us look at a bird we see on just about every game drive, the red billed buffalo weaver. The Red Billed Buffalo Weaver family is unique amongst birds as it has a phalloid organ , not quite a penis and not quite a cloaca either.
In the male this phallus like structure is about 20 mm long, 8 mm at the base and tapers to about 3 mm at the tip.
Scientists believe that this organ evolved in response to sperm competition. The phalloid organ is significantly longer in males that are resident in nests than in those in non-resident males. It is also significantly longer in males with a harem than in those without a harem of females.
These weavers breed colonially and have either a cooperatively polygynadrous (two unrelated males and several females ) or a polygynous (one male and several females ) mating system. This system is also very rare in birds with only a couple of birds in the world breeding this way.
This arrangement provides females with the opportunity to copulate with more than one male and paternity anlyses using DNA reveals that 63% of multiple-offspring broods, comprising 43 offspring in one test, had multiple sires. Sperm competition was therefore intense. Experiments with captive buffalo weavers reveal that the phalloid organ was not intermittent during copulation, but functioned as a stimulatory organ which necessitated protracted copulation in order to induce male orgasm and ejaculation, a feature unique to the species.
In the next article I will chat some more about everyday birds that have something special about them.
Roy can be found in his shop at Casterbridge Lifestyle Centre, Roy Sarkin Jewellers, phone 013 751 2747. Birding is his hobby and he’s delighted to talk avian with any passersby!