Part of the family Columbidae, pigeons show few visible differences between males and females depending on the species. The genus Columba is the most common of all, including feral and domestic pigeons. While it is not easy to observe differences between sexes in most pigeon species, male and female pigeons can differ in size, behaviour, colour patterns and sexual organs.
Male pigeons are slightly bigger and more robust than females. However, it is often difficult to observe size difference between sexes in domestic and wild species, such as the turkey-sized Victoria crowned pigeon (Goura Victoria), which is endemic to New Guinea. The head shape can help to differ males from females. In some species, female pigeons have narrower heads.
In some species, adult males have brighter orange rings around the edge of their irises. Females often have light orange or greenish grey eyes. Domestic and feral pigeons with predominant black patterns and iridescent neck feathers are more likely to be males. Wood pigeon (Columba palumbus) males often have lighter breasts in comparison to females. Endemic to the Fiji islands, Ptilinopus victor is a species featuring distinct colours between sexes: males are bright orange and females are green.
Although the only external sexual organ in both male and female pigeons is the cloaca, which is also used for excretion, internal sexual organs are very distinct between the sexes. Male pigeons produce sperm in two testicles, which become larger during mating season. Females have only one functional ovary, which is linked to a long tube called the oviduct.
The best way to identify the sex of a pigeon is to observe its behaviour. During mating season, males make a distinct and long sound, bow to the floor and open their tails making a semicircle, while females stand upright swelling their plumage. Males also peck the heads of females.