Indiscriminate Interspecific Aggression Leading to Almost Sole Occupancy of Space by a Single Species of Bird

Abstract

SUMMARYDow, D. D. 1977. Indiscriminate interspecific aggression leading to almost sole occupancy of space by a single species of bird. Emu 77: 115–121.Noisy Miners Manorina melanocephala, Australian honeyeaters, reside and feed in dense colonies in open woodland all year. All other species entering these colonies are attacked, sometimes killed. M. melanocephala, through group aggression, successfully defends its colonies against intrusion and settlement by other species of birds. Comparison with scarcer populations in more structurally complex woodland, where the species is less able to eliminate others, suggests that the advantage gained by the interspecific aggression pertains to food resources, because the species forages more in a wider range of feeding zones in areas where possible competitors have been ousted. By eliminating virtually all competitors, M. melanocephala gains exclusive use of all food resources in its colonies. Such interspecific interaction is unique among birds and possibly among animals in general. Also, M. melanocephala breeds communally, i.e. many individuals feed the young in a single nest. Food items given to the young are usually very small and the number of feeding trips to the nest extremely high. This high rate of feeding may be necessitated by the relatively greater abundance of small insects, which in turn could be due to the complete absence of smaller avian competitors.