Do differences in the availability of anthropogenic food resources influence the observed levels of agonistic behaviour in Noisy Miners (Manorina melanocephala)?

Abstract

ABSTRACT The Noisy Miner (Manorina melanocephala) is a cooperative honeyeater living in social groups throughout south-east Australia that displays high levels of interspecific aggression and reduces avifaunal biodiversity in areas it occupies. Human-induced habitat changes have also potentially increased the availability of high-quality habitat and food resources available for Noisy Miners, which may in turn affect activity budgets and the duration or intensity of aggression displayed by Miners towards other species. To quantify the impact of differences in the potential availability of anthropogenic food resources on Noisy Miner aggression levels, we presented taxidermy models from three different categories of bird species (food competitors, non-food competitors and potential predators) and quantified observed aggression in three separate habitats: natural areas with very limited additional anthropogenic food resources, gardens that provided supplementary resources such as nectar-rich ornamental plants, and cafés that provided access to human food items. As predicted, Noisy Miners exhibited agonistic behaviours for a significantly longer period in the habitats with anthropogenic food resources, namely gardens and cafés in comparison to natural areas. The type of model presented also impacted Miner response, with: (1) greater numbers of Miners mobbing predator rather than competitor models, (2) Miners mobbing predator models for longer periods than competitors, and (3) a greater probability of Miners physically contacting competitor models. These findings demonstrate that additional resources have the ability to impact time budgets of species and, for hyperaggressive birds such as Noisy Miners, can impact biodiversity in more nuanced ways than previously quantified.