page_title: Pair bond
section_title: Birds
hierarchical_section_title: Pair bond / Examples / Birds
caption_attribution_description: A pair of Mallard ducks (male and female).
context_page_description: In biology, a pair bond is the strong affinity that develops in some species between a mating pair, often leading to the production and rearing of offspring and potentially a lifelong bond. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary biology circles. The term often implies either a lifelong socially monogamous relationship or a stage of mating interaction in socially monogamous species. It is sometimes used in reference to human relationships.
  Monogamous voles have significantly greater density and distribution of vasopressin receptors in their brain when compared to polygamous voles. These differences are located in the ventral forebrain and the dopamine-mediated reward pathway.
  Peptide arginine vasopressin, dopamine, and oxytocin act in this region to coordinate rewarding activities such as mating, and regulate selective affiliation. These species-specific differences have shown to correlate with social behaviors, and in monogamous prairie voles are important for facilitation of pair bonding.
context_section_description: Close to ninety percent of known avian species are monogamous, compared to five percent of known mammalian species. The majority of monogamous avians form long-term pair bonds which typically result in seasonal mating: these species breed with a single partner, raise their young, and then pair up with a new mate to repeat the cycle during the next season. Some avians such as swans, bald eagles, California condors, and the Atlantic Puffin are not only monogamous, but also form lifelong pair bonds. 
  When discussing the social life of the bank swallow, Lipton and Barash state:
  For about four days immediately prior to egg-laying, when copulations lead to fertilizations, the male bank swallow is very busy, attentively guarding his female. Before this time, as well as after—that is, when her eggs are not ripe, and again after his genes are safely tucked away inside the shells—he goes seeking extra-pair copulations with the mates of other males…who, of course, are busy with defensive mate-guarding of their own.
  In various species, males provide parental care and females mate with multiple males. For example, recent studies show that extra-pair copulation frequently occurs in monogamous birds in which a "social" father provides intensive care for its "social" offspring.
caption: Male (left) and female (right) mallard ducks form seasonal monogamous pairs.
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