Pigeons are monogamous. Eight to 12 days after mating, the females lay 1 or 2 eggs that hatch after 18 days. The male provides nesting material and guards the female and the nest. The young are fed pigeon milk, a liquid-solid substance secreted in the crop of the adult (both male and female) that is regurgitated. The young leave the nest at 4 to 6 weeks of age. More eggs are laid before the first clutch leaves the nest. Breeding may occur during all seasons, but peak reproduction occurs in the spring and fall. A population of pigeons usually consists of equal numbers of males and females. Pigeons mate year-round, but most of the 5 to 6 broods per year are raised during the spring and summer, when temperatures are above freezing.
Pigeons inhabit lofts, steeples, attics, caves, and ornate architectural features of buildings where openings allow for roosting, loafing, and nest building. Nests consist of sticks, twigs, and grasses clumped together to form a crude platform.
In captivity, pigeons commonly live up to 15 years and sometimes longer. In urban populations, however, pigeons seldom live more than 3 or 4 years. Natural mortality factors, such as predation by mammals and other birds, diseases, and stress due to lack of food and water, reduce pigeon populations by approximately 30% annually.
Pigeons are highly dependent on humans to provide them with food and sites for roosting, loafing, and nesting. They are commonly found around farm yards, grain elevators, feed mills, parks, city buildings, bridges, and other structures.
Pigeons are primarily grain and seed eaters and will subsist on spilled or improperly stored grain. They also will feed on garbage, livestock manure, insects, or other food materials provided for them intentionally or unintentionally by people. In fact, in some urban areas the feeding of pigeons is considered a form of recreation. They require about 1 ounce (30 ml) of water daily. They rely mostly on free-standing water but they can also use snow to obtain water.