Neuroendocrine regulation of long-term pair maintenance in the monogamous zebra finch

•Zebra finches have distinct reproductive states with differing sex steroid profiles.•In the laboratory, water restriction induces a non-breeding state in zebra finches.•Sex steroids might interact with other neuromodulators to regulate pair bonding.•Zebra finches are an excellent model system for studying monogamy.

This article is part of a Special Issue “SBN 2014”.Understanding affiliative behavior is critical to understanding social organisms. While affiliative behaviors are present across a wide range of taxa and contexts, much of what is known about the neuroendocrine regulation of affiliation comes from studies of pair-bond formation in prairie voles. This leaves at least three gaps in our current knowledge. First, little is known about long-term pair-bond maintenance. Second, few studies have examined non-mammalian systems, even though monogamy is much more common in birds than in mammals. Third, the influence of breeding condition on affiliation is largely unknown. The zebra finch (Taeniopygia guttata) is an excellent model system for examining the neuroendocrine regulation of affiliative behaviors, including the formation and maintenance of a long-term pair bond. Zebra finches form genetically monogamous pair bonds, which they actively maintain throughout the year. The genomic and neuroanatomical resources, combined with the wealth of knowledge on the ecology and ethology of wild zebra finches, give this model system unique advantages to study the neuroendocrine regulation of pair bonding. Here, we review the endocrinology of opportunistic breeding in zebra finches, the sex steroid profiles of breeding and non-breeding zebra finches (domesticated and wild), and the roles of sex steroids and other signaling molecules in pair-maintenance behaviors in the zebra finch and other monogamous species. Studies of zebra finches and other songbirds will be useful for broadly understanding the neuroendocrine regulation of affiliative behaviors, including pair bonding and monogamy.