The relationship between dominance behaviour, bill size and age group in Greater Sheathbills Chionis alba
A dominance hierarchy developed within a wintering flock of Greater Sheathbills which fed regularly at a concentrated artificial food source. Each bir's dominance position was determined from the proportion of interactions in which it was displaced, and from the number of other birds which it was seen to displace.
Most dominant birds were known to be over 6 or 7 years of age. They had larger bills than their subordinates had and initiated displacement interactions more often. After each interaction the displacer resumed feeding more quickly than the bird it displaced. Although dominant birds had a higher average peck rate, they did not maintain a higher body mass throughout the winter, nor did they show a higher survival rate than their subordinates.