Pigeons

The common urban pigeon found in many cities is also known as a "Rock Dove." Mating for life (unless one dies,) they both take turns incubating the eggs, and parenting the squabs. Notably both parents have a milky substance that appears in their crops to feed the young for a week or so, then they start the swabs on regurgitated food. As they approach time to fly, the father is doing most of the feeding. Pigeons are famous for their military war efforts.