Like many species that are specifically adapted to human-dominated landscapes, the Rock Dove, commonly known as the pigeon, was introduced into North America from Europe in 1606. Although the earliest pigeons were domestic, it wasn't long before the species became naturalized and were breeding on their own. Today, pigeons inhabit nearly any rural or urban landscape. In rural areas, the Rock Dove feeds on waste seeds and grains, although urban Pigeons often rely on human handouts and junk food, including bread, popcorn, donuts and french fries. Nests are built on roofs, ledges, balconies, as well as under bridges, highways, and overpasses. Post-hatch pigeons consume the parents' milk, which is actually a substance produced by the parents' crop. After a week, the milk is replaced by partially-digested seeds which are regurgitated from the parents.