STUDIES ON THE SOCIAL STRUCTURE IN THE GROUP LIFE OF CARRIER PIGEON. I. : SOCIAL RELATIONSHIPS BETWEEN INDIVIDUALS AS KEPT IN A PIGEON PEN

Abstract

1. Ten individuals, 5 males and 5 females, were marked and numbered consecutively. No. 1 Male and No. 2 Female were about 3.5 years old, Nos. 3 and 4 Females about 2 years, Nos. 5 and 6 Females about 1 year, and Nos. 7,8,9 and 10 Males 4 or 5 months. They were divided into five combinations of the same aged individuals and preliminarily reared in five small cages for about two weeks. 2. No. 1 Male dominated No. 2 Female through his superior pecking, and then the relation developed into mating and the female laid two eggs. Both of No. 3 and No. 4 Females laid eggs though they were in a homosexual combination of females, while Nos. 4 and 5 Females laid no eggs under the same conditions. But in the two combinations, Nos. 3 and 5 Females dominated respectively thier mates, Nos. 4 and 6 Females, by pecking them away from food dishes at their feeding time. In combinations of Nos. 7 and 8 Males, and Nos. 9 and 10 Males, as well as of Nos. 7 and 10,and Nos. 8 and 9,there could hardly be found no dominance-subordination relationship, though they vigorously pecked each other at their feeding time. The two individuals of the combinations except that of No. 1 Male and No. 2 Female, however, took up their positions on either side of the small cage almost all day long. 3. The preliminary observation of these combinations gave us a promising opening for further approaches. Namely, we could find it most practical and appropriate to begin our observations with such a flock as of the four youngest males set free in a pigeon pen, and thereafter proceeded with our research, gradually joining the remaining combinations, one by one, in this original flock. 4. These starting individuals, Nos. 7,8,9 and 10 Males, neither encountered to fight nor behaved themselves in such manners as to affect their mutual relation. Moreover, they did not peck one another at all at their feeding time, in contrast with the combinations of them kept in the preliminary small cages. It must be remembered, however, that their food dish was about six times as large as those from which the combinations had been fed. They took a recess together on the upper perch, and fed in flocks showing warning behaviors on the floor. None of them occupied its own definite position on the perch, and they usually kept a certain space between them. When by changce one happened to be too close to another, a mutual pecking took place between them, which might make them keep a sufficient or one of them flew away so as not to be pecked any more. Soon after Nos. 5 and 6 Females joined this flock, a new fact was found that No. 8 Male pursued more actively No. 5 Famale, which usually avoided him, than No. 10 Male did. 5. Since these ten individuals were all set free in the pigeon pen, their movement on the floor became more active than it had been in the smaller flock, though they spent most of their time on the perches. No. 1 Male commenced displaying against every other male or female, which used to be avoided by the latter. Five females, Nos. 2,3,4,5 and 6,tried to make a billing one after another with No. 1 Male, and often succeeded in copulation after billing. Other males, Nos. 7,8,9,and 10,wandered sometimes with incomplete display, near those females, and after a while No. 8 Male consorted himself with No. 3 Female. These relations developed on the floor, while their spacing was executed on each perch and the board. 6. The setting of artificial nests on the perches, however, made an abrupt transition to the most active display of males, by which they perhaps declared their nest-occupations. Thus No. 1 Male and No. 8 Male occupied their nests on either end of the upper perch, and divided the perch into their territories. Then Nos. 1 and 8 introduced Nos. 2 and 3 Females respectively into their own nests C and A, and drove away intruders by pecking or body-checking. Besides, No. 1 Male continued consorting relations with other females except with No. 3 Female only on the floor. Since Nos. 2 an