Despite the ecological importance of pair bonding, the ontogeny of pair bond formation remains poorly understood. We capitalized on long-term high-resolution tracking of social interactions across replicated colonies of captive zebra finches, Taeniopygia guttata, to map the dynamics of social relationships prior to reproduction and to identify the role that relationship quality plays in subsequent reproductive performance. We found that pairs that developed stronger and more stable social relationships outside the breeding season were more likely to breed together and form a pair bond. Moreover, pairs that formed a stable social relationship initiated reproduction faster than those with less stable pair bonds, while the stability and the length of time since establishment of the pair bond both reduced the probability of divorcing. Our results demonstrate an important link between the ontogeny of social relationships and reproductive benefits that may explain the evolution of long-term monogamy.
