Miner stocks continue to rise, closing out small consumers

A large-scale research collaboration has discovered why the native Noisy Miner now dominates bird communities in eastern Australia.

The Noisy Miner, also known as the Soldierbird (Manorina melanocephala), is well known to residents of eastern Australia because it seems to appreciate our landscape designs. Whether in urban or rural settings, this pugnacious Australian honeyeater thrives in the mixture of trees and grasslands that humans tend to nurture. And it is not at all shy and retiring. Noisy Miners have reputations as bullies, attacking birds that are smaller than themselves and driving them from their territories. Our recent research confirms this reputation, showing that Noisy Miners reduce the abundance of small insect and nectar-feeders by more than 50%, even at densities as low as 0.65 miners per hectare.

Several independent research projects have investigated the ecology of Noisy Miners in specific regions of eastern Australia, including an Australian Museum project from the 1990s. And a multi-institutional collaboration that I’m a part of has now combined the data from 23 previous studies, encompassing 2128 sites across Australia, to test models to explain the expansion and dominance of this keystone species.

Our new paper demonstrates that Noisy Miners really are associated with "edge" habitats - from Tasmania to northern Queensland. They are found in both high and low rainfall areas, and although occurring in higher densities in low rainfall areas, their effect on small birds appears to be even greater where there is high rainfall.

Noisy Miners are less likely to inhabit vegetation dominated by trees with needle-shaped leaves, such as native pines and casuarinas, than vegetation with blade-shaped leaves, such as eucalypts. This may be due to differences in insect availability or because many of the common species with needle-shaped leaves are wind-pollinated and do not provide a nectar resource.

Most importantly in terms of environmental impact is our finding that once they occur at densities of more than 0.65 birds per hectare, they have substantial effects on the numbers of small-bodied birds. Noisy Miners are commonly seen at densities of over 10 birds per hectare which is seriously bad news for fairy wrens, honeyeaters, robins and thornbills.

The expansion of Noisy Miner populations into modified habitats continues, and seems to be exacerbated by drought. Noisy Miners are clearly a serious biodiversity problem, and “Aggressive exclusion of birds from woodland and forest habitat by abundant Noisy Miners” has now been listed as a key threatening process both in New South Wales and nationally. We will be looking for ways of combating this threat in a new research project involving experimental removals of Noisy Miners from woodland sites across New South Wales.

Dr Richard Major
Principal Research Scientist, AMRI

More information
Thomson J. R., Maron M., Grey M. J., Catterall C. P., Major R. E., Oliver D. L., Clarke M. F., Loyn R. H., Davidson I., Ingwersen D., Robinson D., Kutt A., MacDonald M. A. & Mac Nally R.  (2015). Avifaunal disarray: quantifying models of the occurrence and ecological effects of a despotic bird species. Diversity and Distributions 21, 451-64. 

Australian Museum: Arresting declines of woodland birds through noisy miner control.

Acknowledgements
Special thanks to Jim Thomson and Ralph Mac Nally for their extraordinary analytical skills, and to Martine Maron for establishing and leading the Noisy Miner Working Group, sponsored by the Australian Centre for Ecological Analysis and Synthesis.