Neuroendocrinology of Affiliative Behavior in a Social Species: The Zebra Finch

Zebra finches (Taeniopygia guttata) are desert-dwelling birds that form long-term pair bonds. Natural droughts and experimental water restriction affect breeding in this species. Sex steroids can regulate courtship and behaviors associated with pair-maintenance in breeding condition zebra finches. However, pair-maintenance in non-breeding condition zebra finches has not been studied. Here, we used water restriction (1mL/subject/week) to bring zebra finch pairs into non-breeding condition. Control pairs were provided with water ad libitum. We examined the effects of water restriction on (1) reproductive physiology (number of eggs laid, gonad size, oviduct length, and sex steroid levels) and (2) pair-maintenance behaviors. Baseline affiliative behaviors were recorded before and after water restriction. After water restriction, we conducted two behavioral tests, (1) a “partner preference test” and (2) a “partner reunion test,” and scored a variety of affiliative behaviors. In females, water restriction strongly decreased the number of eggs laid, follicle size, and oviduct length. In males, however, water restriction did not affect testis size. We are currently measuring plasma and brain steroid levels. In baseline behavioral observations, water restriction decreased time in the nestbox but did not affect other affiliative behaviors. Furthermore, water restriction did not affect behavior during the partner preference test or partner reunion test. These data indicate a sex difference in the physiological effects of water restriction and suggest that pair maintenance behaviors are maintained in non-breeding zebra finch pairs. Future studies will examine the role, if any, of systemic and neurally-synthesized sex steroids in zebra finch affiliative behaviors.