Social behavior in brown-headed cowbirds: Emergence in a complex system

Research into the social behavior of animals is complicated by social behavior's dependence on the context of the social group. Conclusions drawn from experiments performed in highly controlled situations with two or three animals often do not extrapolate to behavior in larger groups as are found in the wild. Social behavior is an emergent property of a group of animals, formed from interactions within the group and not inherent in any one member. The field of complex systems provides both a method for examining behavior in a group, computer simulation, and a new perspective toward research, the recognition of emergent phenomena. Social behavior in brown-headed cowbirds (Molothrus ater) was examined in the context of a group of freely assorting birds with the perspective that the group formed a complex system. The cowbirds produced a self-organized association pattern based on similarity in age and sex. Differences in social associates of juvenile males correlated with their singing behavior and courtship success. Immediate behavior interacted with social context. The social context surrounding a singing male differed from his general social context, and correlated with differences in song repertoires. These phenomena would not be accessible in highly controlled social situations as they were emergent properties of the group of birds, thus had meaning only within the context of the group. A computer simulation was built to evolve individual-based models with a genetic algorithm to match association patterns of real birds. The rules used by the models gave insight into how the real birds may self-organize. By regarding the group of birds as a complex system, aspects of social behavior were examined that would not be evident from experiments in highly controlled social situations. To understand how social behavior operates in a group, the group must be examined as a whole.