The formation and maintenance of socially monogamous pair bonds occurs in over 90% of bird species. Despite this, the majority of research examining the neuroendocrine basis of monogamy has focused pair bond formation in mammals, where monogamy is rare. Zebra finches (Taeniopygia guttata) actively maintain life-long pair bonds, even when not in breeding condition. Zebra finches are opportunistic breeders and their reproduction is highly influenced by unpredictable rainfall. These characteristics make the zebra finch an excellent model for studies of the neuroendocrine regulation of pair bonding. In a series of field and laboratory studies, we explored the potential regulatory role of sex steroids in pair-maintenance behavior at various stages during different the breeding cycle. In the laboratory, we used a combination of steroid manipulations and experimental water restriction to manipulate breeding/endocrine state and determine the effects on pair-maintenance behaviors. In the field, we examined correlations among natural changes in circulating sex steroid levels (assessed via LC-MS/MS), pair-maintenance behaviors, and reproductive success. Taken together, these data will help elucidate the neuroendocrine regulation of social bonding.