STUDIES ON THE SOCIAL STRUCTURE IN THE GROUP LIFE OF CARRIER PIGEON : III. THE DEVELOPMENT OF SOCIAL RELATIONS BETWEEN INDIVIDUALS AS KEPT IN A PIGEON PEN

Abstract

1. The counts of pecking and of being pecked fluctuate periodically and parallel with each other, while those of females vary with less undulation than those of males, as shown in Fig. 1. This seems to indicate the sexual difference in the extent of "peck-activity"rather than that in the mode of "peck-fluctuation". Fig. 1 reveals a still more important fact that the "peck-fluctuation" of younger males is not conspicuous during the early period, but at some points it beings to show high peaks. 2. In each male, there occur one or three remarkable peaks. The week from which they start is different with individuals. At the first peak, each male tries to peck almost all the other individuals, but, at the second and the third peaks, he appears to direct his pecks mainly to the same sex. In addition, he often shows a tendency to try to peck one or a few specified individuals with somewhat more vioient dashes. The relation between males and their objects of pecking is tabulated in Table 1 together with the number of pecking per hour. 3. Table 2 shows the combination of the pairs and the time at which they were formed during the period of observation. No.1 Male had already mated with No.2 Female at the beginning of the observation and No.8 Male mated with No.3 Female at the end of the first week. No. 7 Male mated with No.5 Female at the 9th week. The time of pair-formation agrees fairly well with the first peak in the fluctuation of pecking activity of each male. Establishment of a pair is characterized by the fact that a male pecks his prospective partner persistently before, but seldom after, mating. 4. The critical periods of the affairs such as egg-laying, incubating, hatching of eggs, and rearing offsprings seem to be reflected better in the fluctuation of the pecking number of males than in the pecked number of females. The number of pecking of a male attains peaks before egg-laying of his partner and after hatching of eggs. These relations are also recognized even in the case in which No.1 Male consorted with No.4 Female without forming a pair till the 8th week and the latter laid eggs under such a condition. An exception to this is formed by the pair of No.7 Male and No.5 Female, which failed to incubate their first eggs. The pecked number of females shows somewhat noticeable features only after hatching of eggs and before the next egg-laying throughout the breeding cycle.