モズとアカモズのなわばり関係について

抄録

The interspecific territorialism of two closely related species of shrikes during their breeding periods in two consecutive years, 1959 and 1960,was studied in a small wood (2.3 ha) on our University farm. Each year, in April, the small wood was first occupied by two or three pairs of L. bucephalus, sharing the area. In late May when L. cristatus arrived, these territories entirely collapsed and interspecific as well as intraspecific severe fightings took place for about a week. Then a new division of territories settled their dissensions, resulting in no habitat segregation. The span of each territory was determined by tracing the flying paths of the members of the pair occupying it, and their defensive behavior was tested by placing a stuffed specimen of L. bucephalus on several marginal spots of the territory one after another ; no distinction between intraspecific and interspecific territorial behavior was noticed. We conclude that such an interspecific territorialism may eliminate the effect of competition between the individuals of them, but depress both population levels because they must soare the limited space of common habitat.