Site-Related Dominance and Spacing among Winter Flocks of Black-Capped Chickadees

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Abstract
We studied spacing and social behavior of winter flocks of Black-capped Chickadees (Parus atricapillus) in flood-supplemented and nonsupplemented (control) areas. Flocks of Black-capped Chickadees did not forage in exclusive areas, unlike most other populations of parids. In winters 1985-1986 and 1986-1987, each of 22 feeding stations in the food-supplemented area was visited by two to 10 flocks. Also, at least 50% (1985-1986) and 33% (1986-1987) of the control area was used by two to seven flocks over the winter. When flocks met, agonistic interactions between members of different flocks were less likely than between members of the same flock, suggesting that flocks were not defending areas. However, when agonistic interactions occurred betwen flocks, members of resident flocks dominated intruders. This "site-related dominance" may reflect the ability of flocks to space themselves when conditions favor use of exclusive areas.