The overall objective of this study was to look at the social strategy of domestic fowl living in larger groups use in commercial production systems. The aggressive behaviour of white leghorn female chickens was observed in groups of 15, 30, 60 and 120 in 3, 6, 12 and 24m2 at a constant density of 5 birds/m2. Focal observations of 12 birds per group were carried out from 3 to 18 weeks of age. At all group sizes, aggressive pecking peaked between 6 and 12 weeks and then declined. Regression analysis on means across all ages showed a linear reduction in the frequency of pecks and threats given per focal bird with increasing group size. However, the frequency of pecks and threats received per focal bird showed the opposite pattern, being higher in larger than smaller groups. There was evidence that birds’ to adapt different social strategies with increasing group size. It could be speculated that, while the majority of birds may adapt a tolerant strategy in larger groups, a minority may be despotic, directing aggression indiscriminately towards other birds.