The effect of seed dispersion on the foraging success of dominant and subordinate dark-eyed juncos, Junco hyemalis

Laboratory experiments were conducted to determine the effect of seed dispersion on the rate of seed consumption by dark-eyed juncos, Junco hyemalis, feeding in dyads and in triads. In the dyad experiments, dominants consumed significantly more seeds than subordinates when seeds were clumped in a patch of 0·09 m², but subordinates obtained as many seeds as dominants when food was dispersed in a larger 1·44-m² patch. In the triad experiments, there was a significant difference in seed consumption between dominants, intermediates and subordinates when food was dispersed in patches of 0·09 m² and 1·44 m², but there was no significant difference between ranks when it was dispersed in a larger 2·88-m² patch. Dominants had significantly more agonistic interactions with intermediates than with subordinates. This was not related to differences in distances maintained between birds. Dispersion of seeds in the environment can have a marked effect on whether dominants realize an immediate foraging advantage over subordinates.