Dominance in Winter Flocks of Juncos and Tree Sparrows

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Abstract
Two wild flocks of wintering juncos observed in successive seasons were socially organized in a straight-line pecking order, modified by triangular and reverse-peck relations. A wild flock of tree sparrows feeding with the juncos was socially organized in a straight-line pecking order modified by reverse pecks in one pair-relationship. The juncos had numerous patterns of behavior exemplifying avoidance, tolerance, and dominance. The juncos also displayed unrepeated, individualized sequences of behavior which linked avoidance, tolerance, and dominance in unstereotyped ways. The tree sparrows showed avoidance, tolerance, and dominance in approx. the same ways as did the juncos, but their behavior fell into stereo-typed patterns. In each species fights originated in a special approach for tolerance by a subordinate bird, the result being, if the fight were successful, that the subordinate ate with the dominant. All intra-specific pecking orders were stable, showing no change in social status. The two species were compatible and had an interspecific order of dominance in which the four dominant juncos were subordinate, as a rule, to the 6 subordinate juncos. Irregular contacts and fights were more numerous in interspecific than in intra-specific relations.
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