The genital physiology of the homing pigeon is very interesting to understand. The male is generally larger than the female, but there are also large females.
The male has a dominant behaviour and turns and coos as soon as he sees a female. The male reproductive system consists of two testicles which are located below the kidneys. The testicles produce the spermatozoa needed to fertilise the female's eggs.
The female lays the eggs. She is generally smaller and thinner than the male and rarely coos. She has a single ovary located under the left kidney, the other being atrophied. The ovary produces eggs and oestrogen. As a rule, the ovary releases two eggs, each of which is fertilised by one of the male's sperm cells, but it is possible for the female to lay unfertilised eggs.
During mating, the male sticks his cloaca against the female's cloaca, this step is quick and usually takes less than 30 seconds. The egg, ready to be fertilised, is already attached to the yolk of the egg (vitellus) and is captured by the pinna on the way down to the oviduct. Within a few days, the egg is provided with the various components of the egg before it arrives in the cloaca, ready to be laid through the anus. The pigeon's egg weighs about 20 grams and has a white and rather fragile shell.