Social Hierarchy in Wintering Harris' Sparrows

Dominance has a major role in social organization and has probably important survival value. Dominance is important in decreasing conflicts, regulating population densities, foraging, establishment of territories, reproduction, and care of young. The main objectives of the investigation were to determine (1) the order of dominance; (2) whether or not age, sex and body weight were correlated with social dominance; (3) the status of an individual removed for an interval and then reintroduced into the flock; and (4) the effect upon an established hierarchy by introducing birds of same species, and birds of different species. Thirty-six Harris’ Sparrows, twenty-one adults and fifteen immature, were captured and placed in observation cages. Each cage contained six birds. Other species used in the study were White-crowned Sparrows and an Oregon Junco. A social hierarchy of the “peck-right” type exists among Harris’ Sparrows. Peck-orders were of a linear type with some triangles. Reversals in dominance occurred primarily among the more subordinate birds. Age, sex, weight, and residence in the cages showed no relationship with status in the hierarchies. Slightness of molt may have been a factor influencing dominance. Birds reintroduced after intervals of seven to sixteen day returned to their original positions in their social hierarchies. Status of introduced Harris’ Sparrows was dependent upon the aggressiveness of the new birds. The Harris’ Sparrows, White-crowned Sparrows, and an Oregon Junco behaved as a single flock and had an interspecific hierarchy. White-crowns dominated each flock, and the junco was subordinate to each group.