Non-Kin Infanticide by Male Oriental Magpie Robins in Nest Boxes

Abstract

Although a number of infanticide cases have been recorded among birds, since the incidence of this behavior is, overall, low and difficult to confirm, the importance of infanticide in the cause analysis of breeding failure is likely to be underestimated. During the breeding season of March to August 2019, we observed two cases of non-kin infanticide in Oriental Magpie Robins Copsychus saularis in nest boxes. The first incident occurred during the absence of the nesting male during the brooding period and in the sole presence of the female; another male entered the nest box and continuously attacked and pecked all four eight-day-old nestlings in the nest until they died. A second incident occurred in the presence of both parents, but during the feeding interval; a male perpetrator entered the nest box and pecked and pushed the single three-day-old nestling out of the box. The parents continued to carry food to the nest and tried to feed their nestling even after the latter had been killed. The parents were observed behaving anxiously once they detected no sign of activity from their nestling. We speculated that these examples of non-kin infanticide by conspecific Oriental Magpie Robin males could be attributed to competition for food resources or mates.