The pigeon, a member of the Columbidae family, is one of the most recognized bird species globally, often thriving in urban environments. The process by which these birds reproduce is a complex, co-parented effort that begins long before an egg is laid. This cycle involves specific mating behaviors, shared incubation duties, and a remarkable, specialized feeding method. These unique biological adaptations allow pigeons to be highly successful.
Courtship Rituals and Nest Construction
The reproductive process begins with the male initiating a distinctive courtship display to attract a mate. This ritual involves the male bowing his head, puffing out his chest feathers, and cooing softly as he circles the female. This display signals his suitability as a partner, as pigeons typically form monogamous pairs that often mate for life. Once a pair bond is established, the couple selects a nesting site, usually a secluded area like a building ledge or a niche in a bridge. The male gathers materials, while the female constructs the nest, which is a simple, sometimes flimsy structure of twigs and plant materials arranged into a shallow platform.
Egg Laying and the Incubation Period
Following copulation, the female typically lays a clutch of two small white eggs, with the second egg appearing about a day after the first. She usually lays her first egg within 7 to 10 days after mating. Incubation begins immediately after the first egg is laid and generally lasts between 17 and 19 days. The responsibility for keeping the eggs warm is shared equally between the parents. The female incubates from late afternoon through the night, and the male takes over for the remainder of the day, allowing the female time to feed and rest.
Hatching and the Unique Role of Crop Milk
Hatching is a gradual process where the developing chick, known as a squab, uses a temporary structure called the “egg tooth” to crack the shell. This process, called pipping, can take several hours, and the squab emerges blind, nearly naked, and entirely dependent on its parents. The newly hatched squabs are fed a unique substance called crop milk, produced by both the male and female parent. This secretion is not a true liquid but a semi-solid, pale yellow, curd-like material. Crop milk is formed by the sloughing off of fat- and protein-rich epithelial cells from the lining of the parents’ crop, a specialized pouch in the digestive tract.
Production of this substance is regulated by the hormone prolactin, similar to lactation in mammals, and it is extremely high in nutritional content. Crop milk contains higher levels of protein and fat compared to cow or human milk, providing the concentrated nutrition needed for rapid early growth. The parents regurgitate this material directly into the squab’s mouth, serving as the sole source of nourishment for the first week of life.
From Squab to Fledgling
The high-nutrient crop milk fuels an intense period of development, and the squabs’ eyes typically open around day five. Around day seven, the squabs begin transitioning away from a pure crop milk diet as the parents start mixing in partially digested seeds and grains. The squabs develop rapidly, with pin feathers becoming noticeable by day ten, and by three weeks, they are nearly fully feathered. The parents continue to feed the young birds, but the diet shifts completely to regurgitated adult food as crop milk production ceases. Fledging, when the young bird leaves the nest, usually occurs around 25 to 32 days after hatching, though parents may continue feeding them as they learn to forage.