Variation in the stability of cockatiel (Nymphicus hollandicus) pair relationships: the roles of males, females, and mate compatibility

Abstract

AbstractPair relationships and their emergent properties represent potentially significant sources of proximate and ultimate influence on mating systems, but the study of such relational factors has been rare compared to the volume of literature dedicated to individual-level measures of mate quality. This study assessed variation in the stability of pair relationships in cockatiels (Nymphicus hollandicus) and sought sources for that variation in both the behavior of mated individuals and their compatibility. Pair relationships represent an especially salient aspect of the social system of cockatiels, a socially monogamous species with long-term pairing.In a semi-natural, captive setting, this study compared (1) the social interactions between cockatiel mates to those individuals' interactions with opposite-sex non-mates, (2) the roles of males and females in pair relationships, and (3) the various pairs in their displays of intrapair and extrapair interactions. We also assessed the behavioral features underlying pair relationships by examining the interrelationships among social behaviors within pairs and the degree to which emergent properties structure pair relationships. Interactions between mates, as compared to opposite-sex non-mates, were characterized by closer proximity, greater behavioral synchrony, less aggression, more allopreening, and greater sexual behavior. Males and females displayed little dimorphism in many intrapair and extrapair behaviors; however, males approached and courted their mates more than females did, and males but not females exhibited more intersexual aggression to non-mates than to their mates. Social interactions between mates varied significantly among pairs in ways that reflected variation in the degree of behavioral compatibility between mates. In other words, suites of highly correlated behaviors characterized the interactions between mates such that pairs exhibiting greater affiliative or accordant behaviors exhibited less aggressive or discordant behaviors and vice versa. Emergent properties appeared to play an especially important role in compatibility. By examining significant within-species variation in pair relationships, this study complements the increasing knowledge of mating relationships gained from comparative studies and illustrates the importance of emergent, pair-level behavior in the maintenance of long-term monogamous pair-bonds.