The Bell Miner (Manorina melanophrys, Meliphagidae) is a medium-sized, colonial and co-operatively breeding honeyeater. Recent works show that the Bell Miner presents clear patterns of interspecific competition involving aggressive behaviour against many honeyeaters (Meliphagidae) and other bird species (Loyn et al. 1983; Clarke 1984). Nevertheless, those works have been based on short-term (1 year or less) studies only, and none of them have studied the effect territorial defence has on Bell Miners' fitness. We show how the population of honeyeaters decreased over 7 years at the Sir Colin Mackenzie Zoological Park (Southeastern Victoria, Australia). The decrease of honeyeaters in the study site was correlated with a local increase in the Bell Miner population which has been expanding since at least 1983. This process presumably led to the spatial zonation of Bell Miners and honeyeaters observed at present, while other passerine species show no sensitivity to either the invasion of Bell Miners in the recent past or to the present spatial distribution of the Bell Miner population. Finally, we show that Bell Miner reproductive activity is not affected by their interaction with competitors, which leads us to conclude that the interaction between the Bell Miner and other honeyeaters would be better described as asymmetrical competition.
Keywords: Asymmetrical competition; Bell Miner; Honeyeaters.