In June of 2017, a judge in India declared that peacocks are celibate as they do not mate the usual way. I’ve received several questions from India, asking how peacocks reproduce. Apparently there is some widely believed myth in India that peahens get “pregnant’ by drinking the tears of the peacock. I don’t know if this comes from the Hindi religion or some other source, but you would think that people would know a bit more science. We need to dispense with that myth as well as the term pregnant; when birds have an egg developing in their body, they are considered “gravid” and each egg gets formed and laid in a day.
I suspect that the average person really does not know how birds have sex. OK, here’s how it happens. Most birds do not have developed sex organs as do mammals and reptiles. They have an external opening under the base of their tail called a cloaca, which serves as the place where both waste products are eliminated and sperm is transferred from male to female. Typically, the male bird mounts the female from the back, sometimes standing on her back or tail; the tails are moved in opposite directions and the male’s cloaca meets the female’s and sperm is passed to her (called a “cloacal kiss”.) In the case of swifts, this encounter takes place in mid-air! In waterfowl and large flightless birds like ostriches and rheas, the males do have a penis to help in the process.
Both the testes and ovaries become greatly enlarged during the breeding season and very reduced during the non-breeding season. The reason is that there is no sense in carrying around the extra weight during the winter and migration season
I have observed and have been asked by other observers why a male Mallard is trying to drown a female. What he is doing is trying to mate with her, which takes place in the water. He hops astride her back and grabs her neck with his beak and they copulate. Occasionally, several males, usually unmated ones, will try to mate with one female. This is called “rape flight” and often leads to the exhaustion and death of the female.
Once mating takes place the sperm, which may remain viable for two weeks in the female oviduct, swim up the oviduct to the ovaries where an ovum (egg) is fertilized. The egg now begins its rapid journey toward the cloaca, and within 24 hours the tiny ovum, the size of the period at the end of this sentence, gets surrounded by yolk and albumen, then a shell with its membranes, the shell coloring, and is laid. This process takes a lot of energy as well as nutrients such as calcium, so it’s amazing that some small birds can lay five or six eggs in as many days, their total weight approaching that of the female bird itself!
There are lots of preliminaries to courtship, of course, as there are in many animals. Males need to attract females and they do it with color, song, behavior, fancy nests, or some combination of these. It can become quite complex and even bizarre. Sex is the easy part; attracting the right partner is the trick. Not unlike humans, eh?