Importance of Inherent Suitability, Behavioural Flexibility and Competitiveness in Occupancy of Urban Parks by an Endemic Honeyeater

Abstract

Three factors potentially facilitating avian urban colonisation are: (a) inherent suitability for city environments, (b) limited resource overlap with residents, achieved through resource partitioning or outcompeting residents for shared resources, and (c) behavioural flexibility permitting innovative resource exploitation. We examined the foraging ecology and nest site choice of the Noisy Miner ( Manorina melanocephala) in urban parks in Melbourne, Australia to elucidate which of these three factors was likely to be instrumental in facilitating occupancy of this urban habitat by this native honeyeater. The Noisy Miner was relatively unspecialised in its nest site choice in parks, suggesting that the many suburban parks with branching eucalypts probably provide lots of suitable nest sites for this species. Park-dwelling Noisy Miners appeared to be superior competitors for food to most cohabiting bird species. They were never targets of interspecific aggression, but quite often initiated it against 16 other bird species. Most interactions were attacks and/or chases and 74% displaced the target species’ member. In Melbourne's parks, Noisy Miners foraged for invertebrates mainly: (a) in the sub-canopy on foliage, using hanging and reaching behaviours, and (b) on the ground on bark litter and grass, gleaning in a standing posture. Several cohabiting bird species also gleaned invertebrates on the ground in a similar manner, but all also commonly used other behaviours when foraging on this substrate. No cohabiting species that foraged extensively in the sub-canopy fed substantially on invertebrates there. Thus Noisy Miners could successfully inhabit Melbourne's parks apparently at least partly because: (i) nest site choice was relatively unspecialised; (ii) they flexibly exploited food resources at ground level, unlike exurban conspecifics; (iii) they aggressively dominated possible heterospecific food competitors at ground level; and (iv) they probably experienced fairly limited dietary overlap with cohabiting bird species.