Compound Flock as an Aggregation of the Flocks of Constant Composition in the Great Tit, Parus major L.

Abstract

In the Great Tit, the compound flocks were formed through the aggregation of basic flocks consisting of constant composition. Some characteristics of compound flocks are important for understanding not only the social relationship of basic flocks but also the characteristics of basic flock itself. The compound flocks were observed from October to March and most of them consisted of 15 birds or less, typically of two basic flocks whose ranges partly overlapped. Two basic flocks whose ranges did not overlap were associated with each other through the intermediary of a flock whose range overlapped both their ranges. Thus the association of basic flocks primarily resulted from the overlap of their basic flock ranges. The compound flocks foraged over all or some of the basic flock ranges of the jointed flocks, but eventually broke up into each basic flock. The break-up of compound flocks also was related to the basic flock range. Which flock remains or leaves depended on the place where the break-up occurred. In the break-up of the compound flock within some basic flock range, the home flock of the range remained there, while the other left to its basic flock range. The dominance relationship between members of different basic flocks was site dependent; irrespective of sex and age, the members of a basic flock dominated others while the compound flock was feeding within its own basic flock range, so the prior occupancy of an area is an important factor determining the dominance relationship between members of different basic flocks. Thus, it is concluded that the social relationship of basic flocks is primarily related to their basic flock ranges.