Does the presence of grevilleas and eucalypts in urban gardens influence the distribution and foraging ecology of Noisy Miners?

Noisy Miners have been described as a 'reverse keystone' species, aggressively excluding many bird species from an ever-increasing range of human-dominated landscapes. Understanding the factors influencing the distribution of Noisy Miners is therefore an important research priority. To determine whether a relationship exists between the distribution of Noisy Miners and the vegetation composition of suburban gardens, birds were surveyed according to a factorial design defined by the presence or absence of grevilleas and eucalypts. Contrary to popular expectation, there was no significant association between the abundance of Noisy Miners and the presence of hybrid grevilleas. However, there was a highly significant relationship between the abundance of Noisy Miners and the presence of eucalypts. Analysis of foraging time budgets showed that Noisy Miners consistently spent 25-30% of their foraging time feeding on grevilleas (only in sites in which they were present). Similar amounts of time were spent foraging in eucalypts or in flowering callistemons (when available), and the presence of grevilleas did not result in a reduction in overall commitments to foraging. Noisy Miners also spent substantial amounts of time foraging on open ground. This study does not support the notion that hybrid grevilleas have played a causal role in the spread of Noisy Miners across many suburban areas of eastern Australia. Our results are consistent with the hypothesis that it is the proliferation of lightly-treed open areas that favours the Noisy Miner.