Ecological study of social organization in the Great Tit, Parus major L

Abstract

1. This paper describes home range of the flocks and the dominance relationship between the members of a flock, and attempts to clarify the structure, size and of home range and the factors affecting dominance relationship of the members in a flock.2. The field work was made from the spring of 1968 to the winter of 1974-75 in the Akasaka Palace, Tokyo, Japan. The study area of about 37ha mainly consisted of mixed evergreen and deciduous broad-leaved forest. Virtually all of the birds were marked individually by colour rings and their previous history was known.3. The home range of the flock can be divided into two area. The first is a main area in which the flock foraged over by itself. The second is a secondary area in which the flock moved about with other flocks as compound flock. The size of home range was, in average, 5.5±2.5ha, ranging from 0.7 to 15.9ha.4. The main area is called basic flock range. The flock range can be also divided into two parts; a central part and a peripheral part. The central part was more favourable feeding area than the peripheral one and contained a feeding activity center as most favourable feeding place.5. The flock ranges overlapped each other extensively and were not defended against encroachment of neighbouring flocks. But they were well defined throughout winter and the feeding activity center of neighbouring flocks never overlapped each other.6. The size of flock ranges varied from 0.5 to 3.9ha, with an average of 1.6±0.6ha. It was closely related with the number of adult males in the flock since the flock range was based on the previous breeding territories of adult males belonging to the flock. 7. In the process of flock formation, adults remained their domiciles even after breeding, and then young select the area as their domicile. Therefore, it is concluded that the flock consisted of individuals whose domiciles overlapped and the flock range was the overlapping range of domiciles between members of the flock.8. Adults always dominated over young within a sex group. The important factor determining the dominance relationship was the prior occupancy of the flock range in adults. Males always dominated over females within an age group. This was due to more aggressiveness and larger body size of males.9. The dominance relationship of young within a sex group seemed to be determined before the formation of the flock and remained stable after the flock were formed. The prior occupancy of the flock range and body size were probably important to determine the dominance relationship.10. Adult males were always dominant to young females. This was due to the adult's prior occupancy of the flock range and the dominance of the sex. The dominance relationship between adult females and young males was not unilateral as a whole, but that between a particular adult female and a particular young male was linear and unilateral in a flock. The factor affecting such relation was unknown.11. Although the dominance relationship of adults within a sex group was site dependent, most of the flocks contained one adult male and/or one female and the dominance relationship was linear and unilateral. The relationship was maintained throughout winter and stable over the flock range.12. Taking the dominance relationship into consideration, it is certain that the members of a flock recognized each other individually. The association of members primarily based on the overlap of their domiciles has to be solidified by the individual recognition between the members.