Aim Reports of profound changes in species assemblages brought about by the influence of strongly interacting species are increasingly common. Where these strong interactors are sensitive to anthropogenic habitat changes, relatively small alterations in the environment can result in large and pervasive shifts in assemblages. We review the evidence for widespread assemblage‐level phase shifts across eastern Australia, triggered partly by anthropogenic habitat alteration and mediated by a native, despotic bird: the noisy miner Manorina melanocephala. Location Eastern Australia. Methods Based on the literature, we developed conceptual models of factors affecting site occupancy by, and ecosystem‐level effects of, the noisy miner. We also analysed recent trends in the reporting rate of the noisy miner across its range. Results Individuals of this species cooperate to aggressively exclude almost all smaller bird species from the areas they occupy. The noisy miner is advantaged by habitat fragmentation and structural simplification—habitat changes that facilitate detection and interception of potential competitors by miners. We report that the species is increasingly prevalent, particularly close to forest and woodland edges. Such edges have mainly been created by human land use. The evidence we reviewed showed: (1) strong causal links between the noisy miner and depressed richness and abundance of smaller birds, particularly nectarivores and insectivores; (2) moderate evidence of a positive association with larger bird species; (3) reduced tree condition stemming from impaired control of insect herbivore populations by smaller insectivores; and (4) a plausible negative effect on plant reproduction through reduced tree condition, altered pollination services and altered seed dispersal. Main conclusions This is the first synthesis to document the causes and likely ecological consequences of increasingly prevalent phase shifts catalysed by a despotic species on ecosystems at very large spatial scales (> 1 million km2). Native species affected by human activities can become agents that induce ecological dysfunction.

It has been postulated that aggressive honeyeaters like the noisy miner, Manorina melanocephala, may contribute to rural tree decline by excluding small insectivorous birds from remnant patches of woodland, thereby reducing the level of predation upon defoliating insects. Previous studies provide correlational evidence that avian diversity and abundance is lower in remnant patches of woodland occupied by noisy miners than in those without noisy miners. Noisy miners were removed from three small remnant patches of woodland in north-eastern Victoria. The removal of the majority of noisy miners from a site, or even the removal of only part of a noisy miner colony from a site, resulted in a major influx of honeyeaters and other insectivorous birds to these sites in the following three months. Such major invasions were not observed on matching control sites. At two of the three removal sites, this led to an increase in both the abundance and diversity of birds on the site. At the third site, there was an increase in the diversity, but not the abundance of birds. These experiments are the first to demonstrate that noisy miners affect avian diversity and abundance by aggressive exclusion of small birds. They also showed that if domination by noisy miners is reduced, small, degraded woodland remnants can support significant populations of some small insectivorous birds and honeyeaters. Noisy miners did not reinvade the experimental sites during the following 16 months and avian diversity and abundance remained higher at the experimental sites than at the paired control sites. Long-term monitoring is needed to determine whether the small invading bird species have a lasting effect upon insect populations and tree health.

The abundance of an aggressive Australian honeyeater, the Noisy Miner Manorina melanocephala, was reduced at four small (<8 ha) Grey Box Eucalyptus microcarpa woodland remnants by experimental removal. The diversity and abundance of small insectivorous and nectarivorous birds increased at three of the four sites (relative to matching control sites) over the twelve months following the removal of the Noisy Miners. The one exception occurred at a pair of sites where eucalypts began flowering at one site and finished at the other during the Noisy Miner removal period. These results, taken together with those from three earlier experiments where the abundance of Noisy Miners was reduced in Mugga Ironbark E. Sideroxylon woodland remnants, demonstrate that Noisy Miners affect avian diversity and abundance by aggressive exclusion of other species. In five out of seven experiments, Noisy Miners did not reinvade the small woodland remnants during the ensuing twelve months. When Noisy Miner abundance was reduced, increased populations of small insectivorous and nectarivorous birds used small degraded woodland remnants. Colonizing populations of small birds have the potential to reduce insect infestations and may assist in the recovery of dieback-affected woodland remnants. Research is continuing to test this hypothesis. Reducing the abundance of Noisy Miners in remnant eucalypt woodlands may also be a useful, short-term measure, which could assist in the recovery of threatened or endangered bird species.

AimStrongly interacting species have disproportionately large ecological effects relative to their abundances or biomass. We previously developed two conceptual models that described how one such strong interactor, the Australian bird the noisy miner Manorina melanocephala: (1) establishes resident high‐density and hyperaggressive colonies and (2) in doing so, affects other biota and ecosystem processes. Here, we evaluate parts of those models relating to noisy miner habitat preferences and effects on bird assemblages using data from across the geographical range of the miner.LocationEastern Australia.MethodsAvian‐assemblage data were compiled for 2 128 survey transects (distributed over > 1.3 × 106 km2) and were linked to variables reflecting productivity, local habitat structure and landscape context. Predictors were chosen based on the models, although detailed data for some variables were unavailable at such large scales. We used hierarchical Bayesian models that included observation models to account for different survey effort coupled with potentially nonlinear, spatially‐explicit process models.ConclusionsNoisy miner densities increased with proximity to forest edges (higher densities on forest edges and open sites), in low rainfall areas, and in vegetation dominated by trees with blade‐shaped rather than needle‐shaped leaves. The presence of noisy miners at even relatively small densities (> 0.6 individuals ha−1) depressed both species richness and the abundances of smaller (< 63 g) bird species, by 50% on average. There were positive associations between densities of noisy miners and the abundance and richness of larger‐bodied (> 63 g) bird species. In areas with higher mean rainfall, the associations between noisy miners and small‐ and large‐bird species were more negative and less positive, respectively.

Controlling problem species for conservation can be fraught, particularly when native species are subject to lethal control. The noisy miner (Manorina melanocephala), has been the target of numerous lethal control efforts. Outcomes of these noisy miner removals have varied substantially, so identifying the circumstances under which they are effective is essential for ethical and effective management. We compiled data for all identified noisy miner removals (n = 45), including both permit-based and unofficial removals. We investigated whether methodological and ecological factors explained the effectiveness of removals in reducing noisy miner density or increasing woodland bird richness and abundance. The only predictor of any measure of success was time between first and final culls which was positively related to reduction in noisy miner density. Surprisingly, despite removals mainly failing to reduce noisy miner density to below a threshold above which noisy miners impact smaller birds, woodland birds usually still increased. Disrupted social structure as noisy miners recolonized may have led to less effective aggressive exclusion of small birds. Further removals may not need to reduce noisy miner density to below this threshold to benefit